Effect of replacing Sn4+ ions by Zn2+ ions on structural, optical and magnetic properties of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Selvi, E. Thamarai; Sundar, S. Meenakshi

2017-05-01

This paper highlights on the consequence of replacing tetravalent Sn4+ ions of the SnO2 by divalent Zn2+ ions on their structural, optical, and magnetic properties. Samples of Sn1- x Zn x O2 with x = 0, 0.01, 0.02, 0.03, and 0.04 were synthesized using microwave irradiated solvothermal process. The X-ray powder diffraction patterns reveal the rutile tetragonal phase of all doped SnO2 samples with no secondary phases. The transmission electron microscopy results show the formation of spherical nanoparticles of size 10-30 nm. Morphological changes were observed by scanning electron microscopy. The functional groups were investigated using Fourier transform infrared spectroscopy studies. Optical studies were carried by UV-Vis spectroscopy and fluorescence spectroscopy. Electron paramagnetic resonance was used to calculate the Lande splitting factor ` g'. The magnetic properties using vibrating sample magnetometer exhibit room temperature ferromagnetism for all the samples.

Evaluation of structural, morphological and magnetic properties of CuZnNi (CuxZn0.5-xNi0.5Fe2O4) nanocrystalline ferrites for core, switching and MLCI's applications

NASA Astrophysics Data System (ADS)

Akhtar, Majid Niaz; Khan, Muhammad Azhar; Ahmad, Mukhtar; Nazir, M. S.; Imran, M.; Ali, A.; Sattar, A.; Murtaza, G.

2017-01-01

The influence of Cu substitution on the structural and morphological characteristics of Ni-Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni-Zn nanoferrites. The nanocrystalline ferrites of Cu substituted CuxZn0.5-xNi0.5Fe2O4 ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni-Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu-Zn-Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35-46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M-H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni-Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni-Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI's due to variety of the soft magnetic characteristics.

Morphology-modulation of SnO2 Hierarchical Architectures by Zn Doping for Glycol Gas Sensing and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Zhao, Qinqin; Ju, Dianxing; Deng, Xiaolong; Huang, Jinzhao; Cao, Bingqiang; Xu, Xijin

2015-01-01

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively).

Morphology-modulation of SnO2 Hierarchical Architectures by Zn Doping for Glycol Gas Sensing and Photocatalytic Applications

PubMed Central

Zhao, Qinqin; Ju, Dianxing; Deng, Xiaolong; Huang, Jinzhao; Cao, Bingqiang; Xu, Xijin

2015-01-01

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively). PMID:25597269

Synthesis and enhanced acetone gas-sensing performance of ZnSnO3/SnO2 hollow urchin nanostructures

NASA Astrophysics Data System (ADS)

Lian, Dandan; Shi, Bing; Dai, Rongrong; Jia, Xiaohua; Wu, Xiangyang

2017-12-01

A kind of novel ZnSnO3/SnO2 hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption techniques. The results revealed that many tiny needle-like SnO2 nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO3 hollow microspheres and the ZnSnO3/SnO2 hollow urchin nanostructures with different SnO2 content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO3/SnO2 hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO3/SnO2 hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO3/SnO2 hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO2.

Studying Structural, Optical, Electrical, and Sensing Properties of Nanocrystalline SnO2:Cu Films Prepared by Sol-Gel Method for CO Gas Sensor Application at Low Temperature

NASA Astrophysics Data System (ADS)

Al-Jawad, Selma M. H.; Elttayf, Abdulhussain K.; Saber, Amel S.

Nanocrystalline SnO2 and SnO2:Cu thin films derived from SnCl2ṡ2H2O precursors have been prepared on glass substrates using sol-gel dip-coating technique. The deposited film was 300±20nm thick and the films were annealed in air at 500∘C for 1h. Structural, optical and sensing properties of the films were studied under different preparation conditions, such as Cu-doping concentration of 2%, 4% and 6wt.%. X-ray diffraction studies show the polycrystalline nature with tetragonal rutile structure of SnO2 and Cu:SnO2 thin films. The films have highly preferred orientation along (110). The crystallite size of the prepared samples reduced with increasing Cu-doping concentrations and the addition of Cu as dopants changed the structural properties of the thin films. Surface morphology was determined through scanning electron microscopy and atomic force microscopy. Results show that the particle size decreased as doping concentration increased. The films have moderate optical transmission (up to 82.4% at 800nm), and the transmittance, absorption coefficient and energy gap at different Cu-doping concentration were measured and calculated. Results show that Cu-doping decreased the transmittance and energy gap whereas it increased the absorption coefficient. Two peaks were noted with Cu-doping concentration of 0-6wt.%; the first peak was positioned exactly at 320nm ultraviolet emission and the second was positioned at 430-480nm. Moreover, emission bands were noticed in the photoluminescence spectra of Cu:SnO2. The electrical properties of SnO2 films include DC electrical conductivity, showing that the films have two activation energies, namely, Ea1 and Ea2, which increase as Cu-doping concentration increases. Cudoped nanocrystalline SnO2 gas-sensing material has better sensitivity to CO gas compared with pure SnO2.

Preparation of Cu2ZnSnS4 nano-crystalline powder by mechano-chemical method

NASA Astrophysics Data System (ADS)

Alirezazadeh, Farzaneh; Sheibani, Saeed; Rashchi, Fereshteh

2018-01-01

Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is one of the most promising ceramic materials as an absorber layer in solar cells due to its suitable band gap, high absorption coefficient and non-toxic and environmental friendly constituent elements. In this work, nano-crystalline CZTS powder was synthesized by mechanical milling. Elemental powders of Cu, Zn, Sn and were mixed in atomic ratio of 2:1:1:4 according to the stoichiometry of Cu2ZnSnS4 and then milled in a planetary high energy ball mill under argon atmosphere. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffusion reflectance spectroscopy (DRS). XRD results confirm the formation of single-phase CZTS with kesterite structure after 20 h of milling. Also, the mean crystallite size was about 35 nm. SEM results show that after 20 h of milling, the product has a relatively uniform particle size distribution. Optical properties of the product indicate that the band gap of prepared CZTS is 1.6 eV which is near to the optimum value for photovoltaic solar cells showing as a light absorber material in solar energy applications.

Effects of SnO2, WO3, and ZrO2 addition on the magnetic and mechanical properties of NiCuZn ferrites

NASA Astrophysics Data System (ADS)

Wang, Sea-Fue; Yang, Hsiao-Ching; Hsu, Yung-Fu; Hsieh, Chung-Kai

2015-01-01

In this study, the effects of SnO2, WO3 and ZrO2 addition at levels up to 5 wt% on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. Only Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with a SnO2 addition of ≥3.5 wt% required a densification temperature of 1150 °C, while the others reached maximum densification at 1075 °C. All samples revealed a pure spinel phase and a uniform microstructure, except for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with the WO3 addition, which showed an exaggerated grain growth accompanied with a small amount of needle-shaped Cu0.85Zn0.15WO4 second phase. The fracture mode in the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic revealed a transgranular phase, as the CuO second phase increased the grain boundary strength; the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics sintered with 5 wt% additives showed an intergranular phase. The Vickers hardness and the bending strength of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic were 733.6 and 62.0 MPa, respectively. The Vickers hardness of the ferrite with added SnO2 or ZrO2 showed only a slight improvement, while an apparent change (832.7) was observed with the addition of 5.0 wt% WO3. The bending strength of the ferrite was optimized at 75.7 MPa with 2.0 wt% SnO2 and at 90.5 MPa with 3.5 wt% ZrO2, while that of the ferrite sintered with WO3 added dropped gradually from 62.0 to 47.7 MPa as the amount of WO3 was increased from 0 to 5.0 wt% due to the non-uniform microstructure. The pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic sintered at 1075 °C had an initial permeability of 356.9 and a quality factor of 71.2. The addition of ZrO2 led to a significant increase in the initial permeability (588.4 at 5.0 wt% ZrO2), but a slight decline in the quality factor (56.6 at 5.0 wt% ZrO2).

Nanocrystalline SnO2 formation using energetic ion beam.

PubMed

Mohanty, T; Batra, Y; Tripathi, A; Kanjilal, D

2007-06-01

Nanocrystalline tin oxide (SnO2) thin films grown by RF magnetron sputtering technique were characterized by UV-Visible absorption spectroscopy and Photoluminescence spectroscopy. From atomic force microscopic (AFM) and Glancing angle X-ray diffraction (GAXRD) measurements, the radius of grains was found to be approximately 6+/-2 nm. The thin films were bombarded with 250 keV Xe2+ ion beam to observe the stability of nanophases against radiation. For ion bombarded films, optical absorption band edge is shifted towards red region. Atomic force microscopy studies show that the radius of the grains was increased to approximately 8 +/- 1 nm and the grains were nearly uniform in size. The size of the grains has been reduced after ion bombardment in the case of films grown on Si. During this process, defects such as vacancies, voids were generated in the films as well as in the substrates. Ion bombardment induces local temperature increase of thin films causing melting of films. Ion beam induced defects enhances the diffusion of atoms leading to uniformity in size of grains. The role of matrix on ion beam induced grain growth is discussed.

Effect of various SnO2 pH on ZnO/SnO2-composite film via immersion technique

NASA Astrophysics Data System (ADS)

Malek, M. F.; Mohamed, R.; Mamat, M. H.; Ismail, A. S.; Yusoff, M. M.; Rusop, M.

2018-05-01

ZnO/SnO2-composite film has been synthesized via immersion technique with various pH of SnO2. The pH of SnO2 were varied between 4.5 and 6.5. The optical measurements of the samples were carried out using Varian Cary 5000 UV-Vis spectrophotometer within the range from 350 nm to 800 nm at room temperature in air with a data interval of 1 nm. On the other hand, the optical photoluminescence properties were measured by a photoluminescence spectrometer (PL, model: Horiba Jobin Yvon - 79 DU420A-OE-325) using a He-Cd laser as the excitation source at 325 nm. These highly oriented ZnO/SnO2-composite film are potential for the creation of functional materials, such as the sensors, solar cells and etc.

Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles.

PubMed

Baniasad, Arezou; Ghorbani, Mohsen

2016-05-01

In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35Å. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%. Copyright © 2016 Elsevier B.V. All rights reserved.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

2017-05-01

In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

Interfacial effect on the structural and optical properties of pure SnO2 and dual shells (ZnO; SiO2) coated SnO2 core-shell nanospheres for optoelectronic applications

NASA Astrophysics Data System (ADS)

Selvi, N.; Sankar, S.; Dinakaran, K.

2014-12-01

Nanocrystallites of SnO2 core and dual shells (ZnO, SiO2) coated SnO2 core-shell nanospheres were successfully synthesized by co-precipitation method. The as prepared and annealed samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM) and UV-Vis analysis. XRD pattern confirms the obtained SnO2 core with tetragonal rutile crystalline structure and the shell ZnO with hexagonal structure. FTIR result shows the functional groups present in the samples. The spherical morphology and the formation of the core-shell structures have been confirmed by HRTEM measurements. The UV-Vis showed that band gap is red shifted for as-prepared and the shells coated core-shell samples. From this investigation it can be concluded that the surface modification with different metal and insulating oxides strongly influences the optical properties of the core-shell materials which enhance their potential applications towards optical devices fabrication.

The gas-sensing potential of nanocrystalline SnO2 produced by a mechanochemical milling via centrifugal action

NASA Astrophysics Data System (ADS)

Kersen, Ü.

In this work, the synthesis of undoped nanocrystalline tin dioxide powders and the subsequent preparation of SnO2 thick-films were studied. An initial mixture of SnCl2 and Ca(OH)2 was sealed in a vial for milling in an air atmosphere. Heat treatment of the milled powder resulted in the formation of tetragonal and orthorhombic SnO2 phases, which was confirmed by X-ray diffraction (XRD) analysis. It was found that crystallite size could be controlled by varying the milling time, the rotation speed and the temperature used for the heat treatment. Crystallite sizes in the range 20 to 30 nm (determined by XRD measurements) were obtained. The total pore volume was 0.22 ml/g for a measured particle size of 37 m2/g. No contamination of the powder during milling was found. The response of the prepared thick-films to H2S gas in the concentration range 0.5 to 10 ppm in air was investigated as a function of the preparation conditions. The advantage of mechanochemical synthesis of powder is its relative simplicity, low cost and possibility of obtaining isolated, unagglomerated nanosized grains. It is shown that chemical reactions, which usually occur in the vibratory mill to produce the SnO phase, can also be initiated during a short processing time in the centrifugal mill.

Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

NASA Astrophysics Data System (ADS)

Korhonen, E.; Prozheeva, V.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.; Liu, H.; Izyumskaya, N.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2015-02-01

We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

Nanocrystalline ZnO as a Visible Active Photocatalyst for the Degradation of Benzene-1,4-diol

NASA Astrophysics Data System (ADS)

Ramachandran, Saranya; Sivasamy, A.

We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV-Visible-DRS spectroscopy showed the material to have bandgap energy of 3.22eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

A study of structural, electrical, and optical properties of p-type Zn-doped SnO2 films versus deposition and annealing temperature

NASA Astrophysics Data System (ADS)

Le, Tran; Phuc Dang, Huu; Luc, Quang Ho; Hieu Le, Van

2017-04-01

This study presents a detailed investigation of the structural, electrical, and optical properties of p-type Zn-doped SnO2 versus the deposition and annealing temperature. Using a direct-current (DC) magnetron sputtering method, p-type transparent conductive Zn-doped SnO2 (ZTO) films were deposited on quartz glass substrates. Zn dopants incorporated into the SnO2 host lattice formed the preferred dominant SnO2 (1 0 1) and (2 1 1) planes. X-ray photoelectron spectroscopy (XPS) was used for identifying the valence state of Zn in the ZTO film. The electrical property of ZTO films changed from n-type to p-type at the threshold temperature of 400 °C, and the films achieved extremely high conductivity at the optimum annealing temperature of 600 °C after annealing for 2 h. The best conductive property of the film was obtained on a 10 wt% ZnO-doped SnO2 target with a resistivity, hole concentration, and hole mobility of 0.22 Ω · cm, 7.19  ×  1018 cm-3, and 3.95 cm2 V-1 s-1, respectively. Besides, the average transmission of films was  >84%. The surface morphology of films was examined using scanning electron microscopy (SEM). Moreover, the acceptor level of Zn2+ was identified using photoluminescence spectra at room temperature. Current-voltage (I-V) characteristics revealed the behavior of a p-ZTO/n-Si heterojunction diode.

Deposition and characterization of ZnSe nanocrystalline thin films

NASA Astrophysics Data System (ADS)

Temel, Sinan; Gökmen, F. Özge; Yaman, Elif; Nebi, Murat

2018-02-01

ZnSe nanocrystalline thin films were deposited at different deposition times by using the Chemical Bath Deposition (CBD) technique. Effects of deposition time on structural, morphological and optical properties of the obtained thin films were characterized. X-ray diffraction (XRD) analysis was used to study the structural properties of ZnSe nanocrystalline thin films. It was found that ZnSe thin films have a cubic structure with a preferentially orientation of (111). The calculated average grain size value was about 28-30 nm. The surface morphology of these films was studied by the Field Emission Scanning Electron Microscope (FESEM). The surfaces of the thin films were occurred from small stacks and nano-sized particles. The band gap values of the ZnSe nanocrystalline thin films were determined by UV-Visible absorption spectrum and the band gap values were found to be between 2.65-2.86 eV.

Fabrication and characterization of SnO2/ZnO gas sensors for detecting toluene gas.

PubMed

Min, Byung-Sam; Park, Young-Ho; Lee, Chang-Seop

2014-11-01

This study investigates the use of SnO2, ZnO, Ag, Au, Cu, In, Pd, Ru and carbon black to improve the sensitivity of a gas sensor for detecting toluene gas. Metal-SnO2/ZnO thick films were screen-printed onto Al2O3 substrates with platinum electrodes. The physico-chemical properties of the sensor materials were characterized using SEM/EDS, XRD, and BET analyses. Measuring the electrical resistance of each sensor as a function of the gas concentration determined the sensing characteristics. The sensors were tested using toluene, benzene, xylene, ethanol, methanol, ammonia and trimethylamine vapors with concentrations of 1-2000 ppm. The gas sensing properties of metal-SnO2/ZnO thick films depended on the content and variety of metals and the content of carbon black. The optimum condition of sensor material for toluene gas detection is operation temperature 300 degrees C and when metal catalyst Cu and carbon black were added. The best sensitivity and selectivity for toluene gas at 300 degrees C resulted from doping with 5 wt.% carbon black, 1 wt.% Cu and 20 wt.% ZnO to SnO2.

Temperature and field dependent magnetization studies on nano-crystalline ZnFe2O4 thin films

NASA Astrophysics Data System (ADS)

Sahu, B. N.; Suresh, K. G.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

2018-05-01

Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops.

Chemical and thermal stability of the characteristics of filtered vacuum arc deposited ZnO, SnO2 and zinc stannate thin films

NASA Astrophysics Data System (ADS)

Çetinörgü, E.; Goldsmith, S.

2007-09-01

ZnO, SnO2 and zinc stannate thin films were deposited on commercial microscope glass and UV fused silica substrates using filtered vacuum arc deposition system. During the deposition, the substrate temperature was at room temperature (RT) or at 400 °C. The film structure and composition were determined using x-ray diffraction and x-ray photoelectron spectroscopy, respectively. The transmission of the films in the VIS was 85% to 90%. The thermal stability of the film electrical resistance was determined in air as a function of the temperature in the range 28 °C (RT) to 200 °C. The resistance of ZnO increased from ~ 5000 to 105 Ω when heated to 200 °C, that of SnO2 films increased from 500 to 3900 Ω, whereas that of zinc stannate thin films increased only from 370 to 470 Ω. During sample cooling to RT, the resistance of ZnO and SnO2 thin films continued to rise considerably; however, the increase in the zinc stannate thin film resistance was significantly lower. After cooling to RT, ZnO and SnO2 thin films became practically insulators, while the resistance of zinc stannate was 680 Ω. The chemical stability of the films was determined by immersing in acidic and basic solutions up to 27 h. The SnO2 thin films were more stable in the HCl solution than the ZnO and the zinc stannate thin films; however, SnO2 and zinc stannate thin films that were immersed in the NaOH solution did not dissolve after 27 h.

ZnO and MgZnO Nanocrystalline Flexible Films: Optical and Material Properties

DOE PAGES

Huso, Jesse; Morrison, John L.; Che, Hui; ...

2011-01-01

An emore » merging material for flexible UV applications is Mg x Zn 1 − x O which is capable of tunable bandgap and luminescence in the UV range of ~3.4 eV–7.4 eV depending on the composition x . Studies on the optical and material characteristics of ZnO and Mg 0.3 Zn 0.7 O nanocrystalline flexible films are presented. The analysis indicates that the ZnO and Mg 0.3 Zn 0.7 O have bandgaps of 3.34 eV and 4.02 eV, respectively. The photoluminescence (PL) of the ZnO film was found to exhibit a structural defect-related emission at ~3.316 eV inherent to the nanocrystalline morphology. The PL of the Mg 0.3 Zn 0.7 O film exhibits two broad peaks at 3.38 eV and at 3.95 eV that are discussed in terms of the solubility limit of the ZnO-MgO alloy system. Additionally, external deformation of the film did not have a significant impact on its properties as indicated by the Raman LO-mode behavior, making these films attractive for UV flexible applications.« less

Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

NASA Astrophysics Data System (ADS)

Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

2014-02-01

A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

The enhancement of photovoltaic parameters in dye-sensitized solar cells of nano-crystalline SnO2 by incorporating with large SrTiO3 particles.

PubMed

Aponsu, G M L P; Wijayarathna, T R C K; Perera, I K; Perera, V P S; Siriwardhana, A C P K

2013-05-15

In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I-V characteristic measurements, photocurrent action spectra, dark I-V measurements, Mott-Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable Zn

Structural and optical characterization of p-type highly Fe-doped SnO2 thin films and tunneling transport on SnO2:Fe/p-Si heterojunction

NASA Astrophysics Data System (ADS)

Ben Haj Othmen, Walid; Ben Hamed, Zied; Sieber, Brigitte; Addad, Ahmed; Elhouichet, Habib; Boukherroub, Rabah

2018-03-01

Nanocrystalline highly Fe-doped SnO2 thin films were prepared using a new simple sol-gel method with iron amounts of 5, 10, 15 and 20%. The obtained gel offers a long durability and high quality allowing to reach a sub-5 nm nanocrystalline size with a good crystallinity. The films were structurally characterized through X-ray diffraction (XRD) that confirms the formation of rutile SnO2. High Resolution Transmission Electron Microscopy (HRTEM) images reveals the good crystallinity of the nanoparticles. Raman spectroscopy shows that the SnO2 rutile structure is maintained even for high iron concentration. The variation of the PL intensity with Fe concentration reveals that iron influences the distribution of oxygen vacancies in tin oxide. The optical transmittance results indicate a redshift of the SnO2 band gap when iron concentration increases. The above optical results lead us to assume the presence of a compensation phenomenon between oxygen vacancies and introduced holes following Fe doping. From current-voltage measurements, an inversion of the conduction type from n to p is strongly predicted to follow the iron addition. Electrical characterizations of SnO2:Fe/p-Si and SnO2:Fe/n-Si heterojunctions seem to be in accordance with this deduction. The quantum tunneling mechanism is expected to be important at high Fe doping level, which was confirmed by current-voltage measurements at different temperatures. Both optical and electrical properties of the elaborated films present a particularity for the same iron concentration and adopt similar tendencies with Fe amount, which strongly correlate the experimental observations. In order to evaluate the applicability of the elaborated films, we proceed to the fabrication of the SnO2:Fe/SnO2 homojunction for which we note a good rectifying behavior.

Growth of nanocrystalline Cu2ZnSnS4 thin films using the spray pyrolysis technique and their characterization

NASA Astrophysics Data System (ADS)

Chandel, Tarun; Halaszova, Sona; Prochazka, Michal; Hasko, Daniel; Velic, Dusan; Thakur, Vikas; Dwivedi, Shailendra Kumar; Zaman, M. Buhanuz; Rajaram, Poolla

2018-05-01

Nanocrystalline thin films of Cu2ZnSnS4 (CZTS) were grown on the glass substrates using the spray pyrolysis technique. The films were grown at a substrate temperature of 300 °C after which they were annealed at 350 °C in vacuum. X-ray diffraction (XRD) studies showed that the films crystallized in the kesterite structure. Energy dispersive analysis of X-rays (EDAX) studies showed that the films possess the desired stoichiometry i.e. the proportion of Cu:Zn:Sn:S in the CZTS solid solution is close to 2:1:1:4. Secondary Ions Mass Spectroscopy (SIMS) depth profiling confirmed the uniformity in elemental composition along the depth of the films. SEM studies showed that the films are covered with CZTS particles forming sheet like structures. AFM studies show that the size of the particles on the surface of the films is around 10-15 nm. UV-VIS-NIR transmission spectra were used to determine the optical band gap of the CZTS films which was found to be around 1.55eV.

NO2 Gas Sensing Properties of Multiple Networked ZnGa2O4 Nanorods Coated with TiO2.

PubMed

An, Soyeon; Park, Sunghoon; Ko, Hyunsung; Jin, Changhyun; Lee, Chongmu

2015-01-01

The NO2 gas sensing properties of ZnGa2O4-TiO2 heterostructure nanorods was examined. ZnGa2O4-core/TiO2-shell nanorods were fabricated by the thermal evaporation of a mixture of Zn and GaN powders and the sputter deposition of TiO2. Multiple networked ZnGa2O4-core/TiO2-shell nanorod sensors showed the response of 876% at 10 ppm NO2 at 300 degrees C. This response value at 10 ppm NO2 is approximately 4 times larger than that of bare ZnGa2O4 nanorod sensors. The response values obtained by the ZnGa2O4-core/TiO2-shell nanorods in this study are more than 13 times higher than those obtained previously by the SnO2-core/ZnO-shell nanofibers at 5% NO2. The significant enhancement in the response of ZnGa2O4 nanorods to NO2 gas by coating them with TiO2 can be explained based on the space-charge model.

Vacancy-like defects in nanocrystalline SnO2: influence of the annealing treatment under different atmospheres

NASA Astrophysics Data System (ADS)

Macchi, C.; Ponce, M. A.; Desimone, P. M.; Aldao, C. M.; Somoza, A.

2018-03-01

The study of electronic and chemical properties of semiconductor oxides is motivated by their several applications. In particular, tin oxide is widely used as a solid state gas sensor material. In this regard, the defect structure has been proposed to be crucial in determining the resulting film conductivity and then its sensitivity. Here, the characteristics of vacancy-like defects in nanocrystalline commercial high-purity tin oxide powders and the influence of the annealing treatment under different atmospheres are presented. Specifically, SnO2 nanopowders were annealed at 330 °C under three different types of atmospheres: inert (vacuum), oxidative (oxygen) and reductive (hydrogen). The obtained experimental results are discussed in terms of the vacancy-like defects detected, shedding light to the basic conduction mechanisms, which are responsible for gas detection.

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 ceramics

NASA Astrophysics Data System (ADS)

Jagadeesha Angadi, V.; Anupama, A. V.; Choudhary, Harish K.; Kumar, R.; Somashekarappa, H. M.; Mallappa, M.; Rudraswamy, B.; Sahoo, B.

2017-02-01

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn0.5Zn0.5Fe2O4 samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiating the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe2O3 and ZnFe2O4 phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications.

Electrochemical and fluorescence properties of SnO2 thin films and its antibacterial activity

NASA Astrophysics Data System (ADS)

Henry, J.; Mohanraj, K.; Sivakumar, G.; Umamaheswari, S.

2015-05-01

Nanocrystalline SnO2 thin films were deposited by a simple and inexpensive sol-gel spin coating technique and the films were annealed at two different temperatures (350 °C and 450 °C). Structural, vibrational, optical and electrochemical properties of the films were analyzed using XRD, FTIR, UV-Visible, fluorescence and cyclic voltammetry techniques respectively and their results are discussed in detail. The antimicrobial properties of SnO2 thin films were investigated by agar agar method and the results confirm the antibacterial activity of SnO2 against Escherichia coli and Bacillus.

MicroCub In Flight

NASA Image and Video Library

2018-01-18

The MicroCub, a modified a Bill Hempel 60-percent-scale super cub, approaches for a landing at NASA's Armstrong Flight Research Center. This was the first flight of the MicroCub in which the crew validated the airworthiness of the aircraft.

Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

NASA Astrophysics Data System (ADS)

Kondkar, V.; Rukade, D.; Bhattacharyya, V.

2018-05-01

Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

Optical Properties of ZnO-Alloyed Nanocrystalline Films

DOE PAGES

Che, Hui; Huso, Jesse; Morrison, John L.; ...

2012-01-01

ZnO is emore » merging as one of the materials of choice for UV applications. It has a deep excitonic energy level and a direct bandgap of ~3.4 eV. Alloying ZnO with certain atomic constituents adds new optical and electronic functionalities to ZnO. This paper presents research on M g x Z n 1 − x O and Z n S 1 − x O x nanocrystalline flexible films, which enable tunable optical properties in the deep-UV and in the visible range. The ZnO and Mg 0 .3 Zn 0 .7 O films were found to have bandgaps at 3.35 and 4.02 eV, respectively. The photoluminescence of the Mg 0 .3 Zn 0 .7 O exhibited a bandedge emission at 3.95 eV, and at lower energy 3.38 eV due to the limited solubility inherent to these alloys. ZnS 0 .76 O 0 .24 and ZnS 0 .16 O 0 .84 were found to have bandgaps at 3.21 and 2.65 eV, respectively. The effect of nitrogen doping on ZnS 0 .16 O 0 .84 is discussed in terms of the highly lattice mismatched nature of these alloys and the resulting valence-band modification.« less

The effect of interaction between surface plasmons of gold nanoparticles and optical active centers on luminescence of Eu3+- doped Zn2SnO4 nanocrystals

NASA Astrophysics Data System (ADS)

Thien, Nguyen Duy; Vu, Le Van; Long, Nguyen Ngoc

2018-04-01

The enhancement and quenching of Eu3+ ion emission were investigated in Zn2SnO4:Eu3+@Au (ZTO:Eu3+@Au) nanocomposites. Under 361 nm excitation we revealed the extinction of the intrinsic defect emission and the enhancement of Eu3+ ion emission when Au content in samples is increased, but under excitation wavelength of 394 nm we observed only the suppression of Eu3+ ion emission. The cause of the observed PL behavior is related to the interaction between surface plasmon induced by gold nanoparticles and luminescence centers in the samples.

Template-free hydrothermal synthesis of MgO-TiO2 microcubes toward high potential removal of toxic water pollutants

NASA Astrophysics Data System (ADS)

Chowdhury, Ipsita Hazra; Kundu, Sukanya; Naskar, Milan Kanti

2018-01-01

MgO-TiO2 microcubes were synthesized by a facile template-free hydrothermal method followed by calcination. Different analytical tools such as XRD, DTA/TG, FTIR, N2 adsorption-desorption study, FESEM, TEM and UV-DRS were used to characterize the sample. The FESEM images exhibited cube shaped particles of size 2-4 μm. The MgO-TiO2 microcubes exhibit a high potential removal of toxic Pb (II) ions and photocatalytic degradation of organic dye methyl orange from water. The absorption capacity was determined by changing different experimental conditions. The spontaneity of the reaction was confirmed by thermodynamic study. The prepared MgO-TiO2 microcubes showed superior adsorption capacity up to 2900 mg g-1 for Pb (II) ions, and about 95% of photodegradation of methyl orange (MO), the water pollutants.

Structural, Optical and Ethanol Sensing Properties of Dy-Doped SnO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Shaikh, F. I.; Chikhale, L. P.; Nadargi, D. Y.; Mulla, I. S.; Suryavanshi, S. S.

2018-04-01

We report a facile co-precipitation synthesis of dysprosium (Dy3+) doped tin oxide (SnO2) thick films and their use as gas sensors. The doping percentage (Dy3+) was varied from 1 mol.% to 4 mol.% with the step of 1 mol.%. As-produced material with varying doping levels were sintered in air; and by using a screen printing technique, their thick films were developed. Prior to sensing performance investigations, the films were examined for structural, morphological and compositional properties using x-ray diffraction, a field emission scanning electron microscope, a transmission electron microscope, selected area electron diffraction, energy dispersive analysis by x-rays, Fourier transform infrared spectroscopy and Raman spectroscopic techniques. The structural analyses revealed formation of single phase nanocrystalline material with tetragonal rutile structure of SnO2. The morphological analyses confirmed the nanocrystalline porous morphology of as-developed material. Elemental analysis defined the composition of material in accordance with the doping concentration. The produced sensor material exhibited good response towards different reducing gases (acetone, ethanol, LPG, and ammonia) at different operating temperatures. The present study confirms that the Dy3+ doping in SnO2 enhances the response towards ethanol with reduction in operating temperature. Particularly, 3 mol.% Dy3+ doped sensor exhibited the highest response (˜ 92%) at an operating temperature of 300°C with better selectivity, fast response (˜ 13 s) and recovery (˜ 22 s) towards ethanol.

Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration.

PubMed

Subramanian, Munisamy; Tanemura, Masaki; Hihara, Takehiko; Soga, Tetsuo; Jimbo, Takashi

2011-04-01

The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

Fabrication of GaN doped ZnO nanocrystallines by laser ablation.

PubMed

Gopalakrishnan, N; Shin, B C; Bhuvana, K P; Elanchezhiyan, J; Balasubramanian, T

2008-08-01

Here, we present the fabrication of pure and GaN doped ZnO nanocrystallines on Si(111) substrates by KrF excimer laser. The targets for the ablation have been prepared by conventional ceramic method. The fabricated nanocrystallines have been investigated by X-ray diffraction, photoluminescence and atomic force microscopy. The X-ray diffraction analysis shows that the crystalline size of pure ZnO is 36 nm and it is 41 nm while doped with 0.8 mol% of GaN due to best stoichiometry between Zn and O. Photoluminescence studies reveal that intense deep level emissions have been observed for pure ZnO and it has been suppressed for the GaN doped ZnO structures. The images of atomic force microscope show that the rms surface roughness is 27 nm for pure ZnO and the morphology is improved with decrease in rms roughness, 18 nm with fine crystallines while doped with 1 mol% GaN. The improved structural, optical and morphological properties of ZnO nanocrystalline due to GaN dopant have been discussed in detail.

Characterization and properties of TiO2-SnO2 nanocomposites, obtained by hydrolysis method

NASA Astrophysics Data System (ADS)

Kutuzova, Anastasiya S.; Dontsova, Tetiana A.

2018-04-01

The paper deals with the process of TiO2-SnO2 nanocomposites synthesis utilizing simple hydrolysis method with further calcination for photocatalytic applications. The obtained nanopowders contain 100, 90, 75, 65 and 25 wt% of TiO2. The synthesized nanocomposite samples were analyzed by X-ray diffraction method, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption method. The correlation between structure and morphology of the obtained nanocrystalline composite powders and their sorption and photocatalytic activity towards methylene blue degradation was established. It was found that the presence of SnO2 in the nanocomposites stabilizes the anatase phase of TiO2. Furthermore, sorption and photocatalytic properties of the obtained composites are significantly influenced not only by specific surface area, but also by pore size distribution and mesopore volume of the samples. In our opinion, the results obtained in this study have shown that the TiO2-SnO2 composites with SnO2 content that does not exceed 10% are promising for photocatalytic applications.

Ultrahigh-Performance Cu2ZnSnS4 Thin Film and Its Application in Microscale Thin-Film Lithium-Ion Battery: Comparison with SnO2.

PubMed

Lin, Jie; Guo, Jianlai; Liu, Chang; Guo, Hang

2016-12-21

To develop a high-performance anode for thin-film lithium-ion batteries (TFBs, with a total thickness on the scale of micrometers), a Cu 2 ZnSnS 4 (CZTS) thin film is fabricated by magnetron sputtering and exhibits an ultrahigh performance of 950 mAh g -1 even after 500 cycles, which is the highest among the reported CZTS for lithium storage so far. The characterization and electrochemical tests reveal that the thin-film structure and additional reactions both contribute to the excellent properties. Furthermore, the microscale TFBs with effective footprints of 0.52 mm 2 utilizing the CZTS thin film as anode are manufactured by microfabrication techniques, showing superior capability than the analogous TFBs with the SnO 2 thin film as anode. This work demonstrates the advantages of exploiting thin-film electrodes and novel materials into micropower sources by electronic manufacture methods.

Optimized photodegradation of Bisphenol A in water using ZnO, TiO2 and SnO2 photocatalysts under UV radiation as a decontamination procedure

NASA Astrophysics Data System (ADS)

Abo, Rudy; Kummer, Nicolai-Alexeji; Merkel, Broder J.

2016-09-01

Experiments on photodegradation of Bisphenol A (BPA) were carried out in water samples by means photocatalytic and photo-oxidation methods in the presence of ZnO, TiO2 and SnO2 catalysts. The objective of this study was to develop an improved technique that can be used as a remediation procedure for a BPA-contaminated surface water and groundwater based on the UV solar radiation. The photodegradation of BPA in water performed under a low-intensity UV source mimics the UVC and UVA spectrum of solar radiation between 254 and 365 nm. The archived results reveal higher degradation rates observed in the presence of ZnO than with TiO2 and SnO2 catalysts during 20 h of irradiation. The intervention of the advanced photocatalytic oxidation (PCO) reduces the time of degradation to less than 1 h to reach a degradation rate of 90 % for BPA in water. The study proposes the use of ZnO as a competitor catalyst to the traditional TiO2, providing the most effective treatment of contaminated water with phenolic products.

Effect of Various Catalysts on the Stability of Characteristics of Acetone Sensors Based on Thin Nanocrystalline SnO2 Films

NASA Astrophysics Data System (ADS)

Sevastyanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Khludkova, L. S.; Chernikov, E. V.; Davydova, T. A.

2018-02-01

The results of studies of electrical and gas sensitive characteristics of acetone sensors based on thin nanocrystalline SnO2 films with various catalysts deposited on the surface (Pt/Pd, Au) and introduced into the volume (Au, Ni, Co) are presented. Films containing impurities of gold and 3d-metals were obtained by the method of magnetron sputtering of mosaic targets. Particular attention was paid to the influence of the longterm tests and humidity level on the properties of sensors. It is shown that the sensors with the deposited dispersed gold layers with Au+Ni and, especially, Au+Co additives introduced into the volume are characterized by the increased stability in the process of testing under prolonged exposure to acetone and also under conditions of varying humidity.

Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gareso, P. L., E-mail: pgareso@gmail.com; Rauf, N., E-mail: pgareso@gmail.com; Juarlin, E., E-mail: pgareso@gmail.com

2014-09-25

Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes.more » The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.« less

Magnetically Separable Fe3O4/SnO2/Graphene Adsorbent for Waste Water Removal

NASA Astrophysics Data System (ADS)

Paramarta, V.; Taufik, A.; Saleh, R.

2017-05-01

Our previous study conducted the SnO2 and SnO2/graphene adsorption efficiency in Methylene Blue removal from aqueous solution, however, the difficulty of adsorbent separation from the methylene blue solution limits its efficiency. Therefore, in this work, SnO2 and SnO2/graphene was combined with Fe3O4 to improve the separation process and adsorption performance for removing the organic dyes. Fe3O4/SnO2/grapheme were synthesized by using the co-precipitation method. The graphene content was varied from 1, 3, and 5 weight percent (wt%). The crystalline phase and thermal stability of the samples were characterized by using X- ray Diffraction (XRD) and Thermal Gravimetric Analysis (TGA). The adsorption ability of the samples was investigated by using significant adsorption degradation of MB observed when the graphene in Fe3O4/SnO2 nanocomposite was added. The other parameters such as pH and initial concentration have also been investigated. The reusability was also investigated to study the stability of the samples. The fitting of equilibrium adsorption capacity result indicates that the adsorption mechanism of Fe3O4/SnO2 nanocomposite with graphene tends to follow the Langmuir adsorption isotherm model.

a Facile Synthesis of Fully Porous Tazo Composite and its Remarkable Gas Sensitive Performance

NASA Astrophysics Data System (ADS)

Liang, Dongdong; Liu, Shimin; Wang, Zhinuo; Guo, Yu; Jiang, Weiwei; Liu, Chaoqian; Ding, Wanyu; Wang, Hualin; Wang, Nan; Zhang, Zhihua

The composite of a nanocrystalline SnO2 thick film deposited on an Al-doped ZnO ceramic substrate was firstly proposed. This study also provided a simple, fast and cost effective method to prepare SnO2 thick film and Al-doped ZnO ceramic as well as the final composite. The crystal structure, morphology, composition, pore size distribution and gas sensitivity of the composite were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Barrett-Joyner-Halenda analysis and gas sensitive measurement system. Results indicated that the composite was fully porous consisted of SnO2, ZnO and ZnAl2O4 crystal phases. The macrosized pores generated in the composite could enhance the gas infiltration into the sensing layers effectively. In this way, combining a high gas-transporting-capability and a nanocrystalline SnO2 thick film, the composite showed very impressive performance. The gas sensitivity of the composite was high enough for ethanol vapor with different concentrations, which was comparable to other kinds of reported SnO2 gas sensors, while showing two straight lines with a turning point at 1000ppm. Finally, the gas sensitive mechanism was proposed based on the microstructure and composition of the composite.

Nanocrystalline ZnCO3-A novel sorbent for low-temperature removal of H2S.

PubMed

Balichard, Kevin; Nyikeine, Camille; Bezverkhyy, Igor

2014-01-15

The reactivity of a nanocrystalline ZnCO3 toward H2S (0.2vol% in N2/H2 mixture) at 140-180°C was characterized by thermal gravimetric analysis and by breakthrough curves measurements. We have found that under used conditions transformation of ZnCO3 into ZnS is complete and the rate determining step of the sulfidation is the surface reaction. Such behavior is in strike contrast with that of ZnO whose sulfidation is severely limited by diffusion. The higher reactivity of ZnCO3 in comparison with ZnO is attributed to the different microstructure of ZnS layer formed in these materials after a partial sulfidation. As in ZnO-ZnS transformation the molar volume increases (from 14.5 to 23.8cm(3)/mol), a continuous protective ZnS layer is formed hampering the access of H2S to the non reacted ZnO core. By contrast, in ZnCO3-ZnS transformation the molar volume decreases (from 27.9 to 23.8cm(3)/mol), which produces a discontinuous non-protective ZnS layer enabling a complete transformation of ZnCO3 even at 140°C. The higher reactivity of ZnCO3 results in a considerable increase of the breakthrough sulfur capacity of the carbonate in comparison with oxide. The material has therefore a good potential for being used as a disposable sorbent for H2S capture at low temperature. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of Co 2SnO 4@C core-shell nanostructures with reversible lithium storage

NASA Astrophysics Data System (ADS)

Qi, Yue; Du, Ning; Zhang, Hui; Wu, Ping; Yang, Deren

This paper reports the synthesis of Co 2SnO 4@C core-shell nanostructures through a simple glucose hydrothermal and subsequent carbonization approach. The as-synthesized Co 2SnO 4@C core-shell nanostructures have been applied as anode materials for lithium-ion batteries, which exhibit improved cyclic performance compared to pure Co 2SnO 4 nanocrystals. The carbon matrix has good volume buffering effect and high electronic conductivity, which may be responsible for the improved cyclic performance.

Bio-green synthesis of Fe doped SnO2 nanoparticle thin film

NASA Astrophysics Data System (ADS)

Gattu, Ketan P.; Ghule, Kalyani; Huse, Nanasaheb P.; Dive, Avinash S.; Bagul, Sagar B.; Digraskar, Renuka V.; Sharma, Ramphal; Ghule, Anil V.

2017-05-01

Herein Fe doped SnO2 nanoparticles have been synthesized using simple, cost effective and ecofriendly biosynthesis method, in which remnant water (ideally kitchen waste) collected from soaked Bengal gram beans (Cicer arietinum L.) was used. This extract consists of different bio-molecules which acted as complexing as well as capping agents for synthesis of Fe-doped SnO2 nanoparticles. The X-ray powder diffraction (XRD) and Field-emission scanning electron microscopy (FE-SEM) revealed uniform size distribution with the average size of 6 nm and confirmed the formation of rutile structure with space group (P42/mnm) and nanocrystalline nature of the products with spherical morphology. Further, the gas sensing properties of the materials have been studied in comparison with other gases. The reported gas sensing results are promising, which suggest that the Fe-dopant is a promising noble metal additives to fabricate low cost SnO2 based sensor.

The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

NASA Astrophysics Data System (ADS)

Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

2016-04-01

Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

Structural, dielectric and impedance spectroscopic studies of Ni0.5Zn0.5-xLixFe2O4 nanocrystalline ferrites

NASA Astrophysics Data System (ADS)

Venkatesh, Davuluri; Ramesh, K. V.

2017-09-01

Nanocrystalline lithium substituted Ni-Zn ferrites with composition Ni0.5Zn0.5-xLixFe2O4 (x = 0.00-0.25 in steps of 0.05) were synthesized by the citrate gel auto-combustion method and were sintered at 1000∘C for 4 h in air atmosphere. The structural, dielectric, impedance spectroscopic and magnetic properties were studied by using X-ray diffraction, impedance analyzer and vibrating sample magnetometer respectively. The X-ray diffraction patterns confirm that all samples exhibit a single phase cubic spinel structure. Suitable cation distribution for all compositions has been proposed by using the X-ray diffraction line intensity calculations and the theoretical lattice parameter for each composition was observed in close agreement with the experimental ones and thereby supporting the proposed distribution. An increase in the saturation magnetization was observed up to x = 0.10 level of Li+ substitution and thereafter magnetization reduced for higher concentrations to the highest level of Li+ substitution. The dielectric constant and the DC resistivity of Ni-Zn-Li ferrites were noticed to decrease with increase in the Li+ ion concentration. The impedance spectroscopic studies by using the Cole-Cole plots were studied in order to obtain the relaxation time, grain resistance and grain capacitance. AC conductivity initially remained almost independent of frequency for lower frequencies and thereafter for higher frequencies the AC conductivity increased with increase of Lithium concentration.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules.

PubMed

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-08

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (R air/R gas = 12.8) compared to that (R air/R gas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules

PubMed Central

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-01

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (Rair/Rgas = 12.8) compared to that (Rair/Rgas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors. PMID:26743814

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules

NASA Astrophysics Data System (ADS)

Choi, Hak-Jong; Choi, Seon-Jin; Choo, Soyoung; Kim, Il-Doo; Lee, Heon

2016-01-01

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO2 (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (Rair/Rgas = 12.8) compared to that (Rair/Rgas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors.

Evaluation of SnO2 for sunlight photocatalytic decontamination of water.

PubMed

Aslam, M; Qamar, M Tariq; Ali, Shahid; Rehman, Ateeq Ur; Soomro, M T; Ahmed, Ikram; Ismail, I M I; Hameed, A

2018-07-01

The broad bandgap tin (IV) oxide (SnO 2 ) is the least investigated semiconductor material for photocatalytic water decontamination in sunlight exposure. A detailed study covering the synthesis, characterization and the evaluation of photocatalytic activity of SnO 2 , in the natural sunlight exposure, is presented. The structural characterization by XRD revealed the formation of phase pure tetragonal SnO 2 with the average crystallite size of ∼41.5 nm whereas minor Sn 2+ states in the material were identified by XPS analysis. As explored by diffuse reflectance (DR) and photoluminescence (PL) spectroscopy, the material exhibited a distinct absorption edge at ∼3.4 eV. The morphological and microstructure analysis of the synthesized SnO 2 was carried out by FESEM and HRTEM. The electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP) predicted the better charge transport and retention ability of the material under illumination whereas the Mott-Schottky extrapolation prophesied the n-type behavior with the flat-band potential of -0.60 V. The photocatalytic activity of SnO 2 was assessed in the exposure of complete spectrum natural sunlight for the removal of 2,4,6-trichlorophenol. The HPLC and TOC analysis monitored the progress of degradation and mineralization whereas the released chloride ions were evaluated by ion chromatography. The effect of the transition metal ions (Fe 3+ , Cu 2+ , Ni 2+, and Zn 2+ ) as electron capture agents and H 2 O 2 as ROS generator was explored during the degradation process. The utility of the material for the simultaneous removal of chlorophenols in the mixture was also investigated. The SnO 2 exhibited sustained activity in the repeated use. Based on experimental evidence congregated, the mechanism of the removal process and the efficacy of SnO 2 for sunlight photocatalytic decontamination of water was established. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structure of the SnO2(110 ) -(4 ×1 ) Surface

NASA Astrophysics Data System (ADS)

Merte, Lindsay R.; Jørgensen, Mathias S.; Pussi, Katariina; Gustafson, Johan; Shipilin, Mikhail; Schaefer, Andreas; Zhang, Chu; Rawle, Jonathan; Nicklin, Chris; Thornton, Geoff; Lindsay, Robert; Hammer, Bjørk; Lundgren, Edvin

2017-09-01

Using surface x-ray diffraction (SXRD), quantitative low-energy electron diffraction (LEED), and density-functional theory (DFT) calculations, we have determined the structure of the (4 ×1 ) reconstruction formed by sputtering and annealing of the SnO2(110 ) surface. We find that the reconstruction consists of an ordered arrangement of Sn3O3 clusters bound atop the bulk-terminated SnO2(110 ) surface. The model was found by application of a DFT-based evolutionary algorithm with surface compositions based on SXRD, and shows excellent agreement with LEED and with previously published scanning tunneling microscopy measurements. The model proposed previously consisting of in-plane oxygen vacancies is thus shown to be incorrect, and our result suggests instead that Sn(II) species in interstitial positions are the more relevant features of reduced SnO2(110 ) surfaces.

Gas Sensing Properties of ZnO-SnO2 Nanostructures.

PubMed

Chen, Weigen; Li, Qianzhu; Xu, Lingna; Zeng, Wen

2015-02-01

One-dimensional (1D) semiconductor metal oxide nanostructures have attracted increasing attention in electrochemistry, optics, magnetic, and gas sensing fields for the good properties. N-type low dimensional semiconducting oxides such as SnO2 and ZnO have been known for the detection of inflammable or toxic gases. In this paper, we fabricated the ZnO-SnO2 and SnO2 nanoparticles by hydrothermal synthesis. Microstructure characterization was performed using X-ray diffraction (XRD) and surface morphologies for both the pristine and doped samples were observed using field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Then we made thin film gas sensor to study the gas sensing properties of ZnO-SnO2 and SnO2 gas sensor to H2 and CO. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO2 and ZnO toward H2 and CO over that of the commonly applied undecorated SnO2 nanoparticles. The improved gas sensing properties are attributed to the size of grains and pronounced electron transfer between the compound nanostructures and the absorbed oxygen species as well as to the heterojunctions of the ZnO nanoparticles to the SnO2 nanoparticles, which provide additional reaction rooms. The results represent an advance of compound nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials, offering a new avenue and direction to detect gases of interest based on composite tin oxide nanoparticles.

Dopant controlled photoinduced hydrophilicity and photocatalytic activity of SnO2 thin films

NASA Astrophysics Data System (ADS)

Talinungsang; Dhar Purkayastha, Debarun; Krishna, M. Ghanashyam

2018-07-01

The influence of Fe and Ni (1 wt.%) doping on the wettability and photocatalytic activity of sol-gel derived SnO2 films is reported. X-ray diffraction studies revealed the presence of tetragonal phase for both pure and doped SnO2 thin films. The crystallite size was of the order of 8 nm indicating the nanocrystalline nature of the films. The pure SnO2 films which were hydrophilic with a contact angle of 11.8° showed increase in contact angle with doping (38.7° for Fe and 48.6° for Ni). This is accompanied by decrease in surface energy and root mean square roughness, with doping of SnO2 film. In order to further increase the water contact angle, the film surfaces were modified using a layer of stearic acid. As a consequence, the water contact angles increased to 108°, 110° and 111° for the pure, Fe and Ni doped SnO2 films respectively, rendering them hydrophobic. Significantly, the unmodified surfaces that did not exhibit any change under UV irradiation showed photoinduced hydrophilicity on modification with stearic acid. There was a red-shift in the optical band gap of SnO2 films from 3.8 to 3.5 eV with doping, indicating the possibility of dopant controlled photocatalytic activity. This was confirmed by observing the photocatalytic degradation of an aqueous solution of methylene blue under UV irradiation. There was, indeed, significant improvement in the photocatalytic efficiency of the metal doped SnO2 thin film in comparison to undoped film. The current work, thus, demonstrates a simple method to chemically engineer the wettability and photocatalytic activity of SnO2 thin film surfaces.

Comparison of Photocatalytic Performance of Different Types of Graphene in Fe3O4/SnO2 Composites

NASA Astrophysics Data System (ADS)

Paramarta, Valentinus; Taufik, Ardiansyah; Saleh, Rosari

2017-03-01

We have reported the role of annealing temperature Fe3O4/SnO2 nanocomposites as a photocatalyst for remove methylene blue (MB) dye from aqueous solution. However, how to enhanced the degradation performance of Fe3O4/SnO2 nanocomposites is important to its photocatalytic application. Therefore, in this work Fe3O4/SnO2 nanocomposites was combined with two different types of graphene materials (NGP and grahene) to improve the photocatalytic performance for remove methylene blue (MB) dye. Fe3O4/SnO2/NGP and Fe3O4/SnO2/graphene have been successfully synthesized by co-precipitation method. The influence of two types graphene on Fe3O4/SnO2 nanocomposites properties were systematically investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). Degradation of methylene Blue (MB) in aqueous solution was studied in detail under photocatalytic process. Effect of catalyst dosage (0.1-0.4 g/L) and scavengers on dye degradation were carried out to check the efficiency of photocatalyst. The results indicated Fe3O4/SnO2/graphene displayed higher photocatalytic activity than other catalyst. The reusability tests have also been done to ensure the stability of the used photocatalyst.

Preparation and characterization of SnO2 and Carbon Co-coated LiFePO4 cathode materials.

PubMed

Wang, Haibin; Liu, Shuxin; Huang, Yongmao

2014-04-01

The SnO2 and carbon co-coated LiFePO4 cathode materials were successfully synthesized by solid state method. The microstructure and morphology of LiFePO4 composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscope. The results showed that the SnO2 and carbon co-coated LiFePO4 cathode materials exhibited more uniform particle size distribution. Compared with the uncoated LiFePO4/C, the structure of LiFePO4 with SnO2 and carbon coating had no change. The existence of SnO2 and carbon coating layer effectively enhanced the initial discharge capacity. Among the investigated samples, the one with DBTDL:LiFePO4 molar ratios of 7:100 exhibited the best electrochemical performance.

Composite tin and zinc oxide nanocrystalline particles for enhanced charge separation in sensitized degradation of dyes.

PubMed

Bandara, J; Tennakone, K; Jayatilaka, P P B

2002-10-01

Composite ZnO/SnO2 catalyst has been studied for the sensitized degradation of dyes e.g. Eosin Y (2', 4', 5', 7'-tetrabromofluorescein disodium salt) in relation to efficient charge separation properties of the catalyst. Improved photocatalytic activity was observed in the case of ZnO/SnO2 composite catalyst compared to the catalytic activity of ZnO, SnO2 or TiO2 powder. The suppression of charge recombination in the composite ZnO/SnO2 catalyst led to higher catalytic activity for the degradation of Eosin Y. Degradation of Eosin follows concomitant formation of CO2 and formation of CO2 followed a pseudo-first-order rate. Photoelectrochemical cells constructed using SnO2, ZnO, ZnO/SnO2 sensitized with Eosin Y showed V(oc) of 175, 306, 512 mV/cm2 and I(sc) of 50, 70, 200 microA/cm2 respectively. A higher irreversible degradation of Eosin Y and higher V(oc) observed on composite ZnO/SnO2 than ZnO and SnO2 separately can be considered as a proof of enhanced charge separation of ZnO/SnO2 catalyst. Eosin Y showed a higher emission decreases on ZnO/SnO2 composite than on individual ZnO, SnO2 or TiO2 indicating dominance of the charge injection process. Photoinjected electrons are tunneled from ZnO to SnO2 particles accumulating injected electrons in the conduction bands allowing wider separation of excited carriers.

Structural analysis of nanocrystalline ZnTe alloys synthesized by melt quenching technique

NASA Astrophysics Data System (ADS)

Singh, Harinder; Singh, Tejbir; Thakur, Anup; Sharma, Jeewan

2018-05-01

Nanocrystalline ZnxTe100-x (x=0, 5, 20, 30, 40, 50) alloys have been synthesized using melt quenching technique. Energy-dispersive X-Ray spectroscopy (EDS) has been used to verify the elemental composition of samples. Various absorption modes are recorded from Fourier transform infrared spectroscopy (FTIR) confirming the formation of ZnTe. The structural study has been performed using X-Ray Diffraction (XRD) method. All synthesized samples have been found to be nanocrystalline in nature with average crystallite size in the range from 49.3 nm to 77.1 nm. Results have shown that Zn0Te100 exhibits hexagonal phase that transforms into a cubic ZnTe phase as the amount of zinc is increased. Pure ZnTe phase has been obtained for x = 50. The texture coefficient (Tc) has been calculated to find the prominent orientations of different planes.

The improvement of gas-sensing properties of SnO2/zeolite-assembled composite

NASA Astrophysics Data System (ADS)

Sun, Yanhui; Wang, Jing; Li, Xiaogan; Du, Haiying; Huang, Qingpan

2018-05-01

SnO2-impregnated zeolite composites were used as gas-sensing materials to improve the sensitivity and selectivity of the metal oxide-based resistive-type gas sensors. Nanocrystalline MFI type zeolite (ZSM-5) was prepared by hydrothermal synthesis. Highly dispersive SnO2 nanoparticles were then successfully assembled on the surface of the ZSM-5 nanoparticles by using the impregnation methods. The SnO2 nanoparticles are nearly spherical with the particle size of 10 nm. An enhanced formaldehyde sensing of as-synthesized SnO2-ZSM-5-based sensor was observed whereas a suppression on the sensor response to other volatile organic vapors (VOCs) such as acetone, ethanol, and methanol was noticed. The possible reasons for this contrary observation were proposed to be related to the amount of the produced water vapor during the sensing reactions assisted by the ZSM-5 nanoparticles. This provides a possible new strategy to improve the selectivity of the gas sensors. The effect of the humidity on the sensor response to formaldehyde was investigated and it was found the higher humidity would decrease the sensor response. A coating layer of the ZSM-5 nanoparticles on top of the SnO2-ZSM-5-sensing film was thus applied to further improve the sensitivity and selectivity of the sensor through the strong adsorption ability to polar gases and the "filtering effect" by the pores of ZSM-5.

Synthesis and Behavior of Cetyltrimethyl Ammonium Bromide Stabilized Zn1+xSnO3+x (0 ≤ x ≤1) Nano-Crystallites

PubMed Central

Placke, Astrid; Kumar, Ashok; Priya, Shashank

2016-01-01

We report synthesis of cetyltrimethyl ammonium bromide (CTAB) stabilized Zn1+xSnO3+x (0 ≤ x ≤1) nano-crystallites by facile cost-effective wet chemistry route. The X-ray diffraction patterns of as-synthesized powders at the Zn/Sn ratio of 1 exhibited formation of ZnSn(OH)6. Increasing the Zn/Sn ratio further resulted in the precipitation of an additional phase corresponding to Zn(OH)2. The decomposition of these powders at 650°C for 3h led to the formation of the orthorhombic phase of ZnSnO3 and tetragonal SnO2-type phase of Zn2SnO4 at the Zn/Sn ratio of 1 and 2, respectively, with the formation of their mixed phases at intermediate compositions, i.e., at Zn/Sn ratio of 1.25, 1.50 and 1.75, respectively. The lattice parameters of orthorhombic and tetragonal phases were a ~ 3.6203 Å, b ~ 4.2646 Å and c ~ 12.8291Å (for ZnSnO3) and a = b ~ 5.0136 Å and c ~ 3.3055Å (for Zn2SnO4). The transmission electron micrographs revealed the formation of nano-crystallites with aspect ratio ~ 2; the length and thickness being 24, 13 nm (for ZnSnO3) and 47, 22 nm (for Zn2SnO4), respectively. The estimated direct bandgap values for the ZnSnO3 and Zn2SnO4 were found to be 4.21 eV and 4.12 eV, respectively. The ac conductivity values at room temperature (at 10 kHz) for the ZnSnO3 and Zn2SnO4 samples were 8.02 × 10−8 Ω-1 cm-1 and 6.77 × 10−8 Ω-1 cm-1, respectively. The relative permittivity was found to increase with increase in temperature, the room temperature values being 14.24 and 25.22 for the samples ZnSnO3 and Zn2SnO4, respectively. Both the samples, i.e., ZnSnO3 and Zn2SnO4, exhibited low values of loss tangent up to 300 K, the room temperature values being 0.89 and 0.72, respectively. A dye-sensitized solar cell has been fabricated using the optimized sample of zinc stannate photo-anode, i.e., Zn2SnO4. The cyclic voltammetry revealed oxidation and reduction around 0.40 V (current density ~ 11.1 mA/cm2) and 0.57 V (current density– 11.7 mA/cm2) for Zn2SnO4

Thermoluminescent properties of nanocrystalline ZnTe thin films: Structural and morphological studies

NASA Astrophysics Data System (ADS)

Rajpal, Shashikant; Kumar, S. R.

2018-04-01

Zinc Telluride (ZnTe) is a binary II-VI direct band gap semiconducting material with cubic structure and having potential applications in different opto-electronic devices. Here we investigated the effects of annealing on the thermoluminescence (TL) of ZnTe thin films. A nanocrystalline ZnTe thin film was successfully electrodeposited on nickel substrate and the effect of annealing on structural, morphological, and optical properties were studied. The TL emission spectrum of as deposited sample is weakly emissive in UV region at ∼328 nm. The variation in the annealing temperature results into sharp increase in emission intensity at ∼328 nm along with appearance of a new peak at ∼437 nm in visible region. Thus, the deposited nanocrystalline ZnTe thin films exhibited excellent thermoluminescent properties upon annealing. Furthermore, the influence of annealing (annealed at 400 °C) on the solid state of ZnTe were also studied by XRD, SEM, EDS, AFM. It is observed that ZnTe thin film annealed at 400 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

In situ studies of ion irradiated inverse spinel compound magnesium stannate (Mg 2SnO 4)

NASA Astrophysics Data System (ADS)

Xu, P.; Tang, M.; Nino, J. C.

2009-06-01

Magnesium stannate spinel (Mg 2SnO 4) was synthesized through conventional solid state processing and then irradiated with 1.0 MeV Kr 2+ ions at low temperatures 50 and 150 K. Structural evolutions during irradiation were monitored and recorded through bright field images and selected-area electron diffraction patterns using in situ transmission electron microscopy. The amorphization of Mg 2SnO 4 was achieved at an ion dose of 5 × 10 19 Kr ions/m 2 at 50 K and 10 20 Kr ions/m 2 at 150 K, which is equivalent to an atomic displacement damage of 5.5 and 11.0 dpa, respectively. The spinel crystal structure was thermally recovered at room temperature from the amorphous phase caused by irradiation at 50 K. The calculated electronic and nuclear stopping powers suggest that the radiation damage caused by 1 MeV Kr 2+ ions in Mg 2SnO 4 is mainly due to atomic displacement induced defect accumulation. The radiation tolerance of Mg 2SnO 4 was finally compared with normal spinel MgAl 2O 4.

Wear behavior of Cu-Zn alloy by ultrasonic nanocrystalline surface modification.

PubMed

Cho, In Shik; Amanov, Auezhan; Ahn, Deok Gi; Shin, Keesam; Lee, Chang Soon; Pyoun, Young-Shik; Park, In-Gyu

2011-07-01

The ultrasonic nanocrystalline surface modification (UNSM) was applied to disk specimens made of Cu-Zn alloy in order to investigate the UNSM effects under five various conditions on wear of deformation twinning. In this paper, ball-on-disk test was conducted, and the results of UNSM-treated specimens showed that surface layer dislocation density and multi-directional twins were abruptly increased, and the grain size was altered into nano scale. UNSM delivers force onto the workpiece surface 20,000 times per second with 1,000 to 4,000 contact counts per square millimeter. The UNSM technology creates nanocrystalline and deformation twinning on the workpiece surface. One of the main concepts of this study is that defined phenomena of the UNSM technology, and the results revealed that nanocrystalline and deformation twinning depth might be controlled by means of impact energy of UNSM technology. EBSD and TEM analyses showed that deformation layer was increased up to 268 microm, and initial twin density was 0.001 x 10(6) cm(-2) and increased up to 0.343 x 10(6) cm(-2). Wear volume loss was also decreased from 703 x 10(3) mm3 to 387 x 10(3) mm3. Wear behavior according to deformation depth was observed under three different combinations. This is related to deformation depth which was created by UNSM technology.

Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles.

PubMed

Lavanya, N; Radhakrishnan, S; Sekar, C

2012-01-01

Ni doped SnO(2) nanoparticles (0-5 wt%) have been prepared by a simple microwave irradiation (2.45 GHz) method. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of rutile structure with space group (P(42)/mnm) and nanocrystalline nature of the products with spherical morphology. Direct electrochemistry of horseradish peroxidase (HRP)/nano-SnO(2) composite has been studied. The immobilized enzyme retained its bioactivity, exhibited a surface confined, reversible one-proton and one-electron transfer reaction, and had good stability, activity and a fast heterogeneous electron transfer rate. A significant enzyme loading (3.374×10(-10) mol cm(-2)) has been obtained on nano-Ni doped SnO(2) as compared to the bare glassy carbon (GC) and nano-SnO(2) modified surfaces. This HRP/nano-Ni-SnO(2) film has been used for sensitive detection of H(2)O(2) by differential pulse voltammetry (DPV), which exhibited a wider linearity range from 1.0×10(-7) to 3.0×10(-4)M (R=0.9897) with a detection limit of 43 nM. The apparent Michaelis-Menten constant (K(M)(app)) of HRP on the nano-Ni-SnO(2) was estimated as 0.221 mM. This excellent performance of the fabricated biosensor is attributed to large surface-to-volume ratio and Ni doping into SnO(2) which facilitate the direct electron transfer between the redox enzyme and the surface of electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

Properties of Resistive Hydrogen Sensors as a Function of Additives of 3 D-Metals Introduced in the Volume of Thin Nanocrystalline SnO2 Films

NASA Astrophysics Data System (ADS)

Sevast'yanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Sergeichenko, N. V.; Chernikov, E. V.; Almaev, A. V.; Kushnarev, B. O.

2017-11-01

Analysis of the results of studying electrical and gas sensitive characteristics of the molecular hydrogen sensors based on thin nanocrystalline SnO2 films coated with dispersed Au layers and containing Au+Ni and Au+Co impurities in the bulk showed that the characteristics of these sensors are more stable under the prolonged exposure to hydrogen in comparison with Au/SnO2:Sb, Au films modified only with gold. It has been found that introduction of the nickel and cobalt additives increases the band bending at the grain boundaries of tin dioxide already in freshly prepared samples, which indicates an increase in the density Ni of the chemisorbed oxygen. It is important that during testing, the band bending eφs at the grain boundaries of tin dioxide additionally slightly increases. It can be assumed that during crystallization of films under thermal annealing, the 3d-metal atoms in the SnO2 volume partially segregate on the surface of microcrystals and form bonds with lattice oxygen, the superstoichiometric tin atoms are formed, and the density Ni increases. If the bonds of oxygen with nickel and cobalt are stronger than those with tin, then, under the prolonged tests, atomic hydrogen will be oxidized not by lattice oxygen, but mainly by the chemisorbed one. In this case, stability of the sensors' characteristics increases.

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

NASA Astrophysics Data System (ADS)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Bouquet-Like Mn2SnO4 Nanocomposite Engineered with Graphene Sheets as an Advanced Lithium-Ion Battery Anode.

PubMed

Rehman, Wasif Ur; Xu, Youlong; Sun, Xiaofei; Ullah, Inam; Zhang, Yuan; Li, Long

2018-05-30

Volume expansion is a major challenge associated with tin oxide (SnO x ), which causes poor cyclability in lithium-ion battery anode. Bare tin dioxide (SnO 2 ), tin dioxide with graphene sheets (SnO 2 @GS), and bouquet-like nanocomposite structure (Mn 2 SnO 4 @GS) are prepared via hydrothermal method followed by annealing. The obtained composite material presents a bouquet structure containing manganese and tin oxide nanoparticle network with graphene sheets. Benefiting from this porous nanostructure, in which graphene sheets provide high electronic pathways to enhance the electronic conductivity, uniformly distributed particles offer accelerated kinetic reaction with lithium ion and reduced volume deviation in the tin dioxide (SnO 2 ) particle during charge-discharge testing. As a consequence, ternary composite Mn 2 SnO 4 @GS showed a high rate performance and outstanding cyclability of anode material for lithium-ion batteries. The electrode achieved a specific capacity of about 1070 mA h g -1 at a current density of 400 mA g -1 after 200 cycles; meanwhile, the electrode still delivered a specific capacity of about 455 mA h g -1 at a high current density of 2500 mA g -1 . Ternary Mn 2 SnO 4 @GS material could facilitate fabrication of unique structure and conductive network as advanced lithium-ion battery.

One-Pot Green Synthesis of Ag-Decorated SnO2 Microsphere: an Efficient and Reusable Catalyst for Reduction of 4-Nitrophenol.

PubMed

Hu, Min; Zhang, Zhenwei; Luo, Chenkun; Qiao, Xiuqing

2017-12-01

In this paper, hierarchical Ag-decorated SnO 2 microspheres were synthesized by a facile one-pot hydrothermal method. The resulting composites were characterized by XRD, SEM, TEM, XPS, BET, and FTIR analysis. The catalytic performances of the samples were evaluated with the reduction of 4-nitrophenol to 4-aminophenol by potassium borohydride (KBH 4 ) as a model reaction. Time-dependent experiments indicated that the hierarchical microspheres assembled from SnO 2 and Ag nanoparticles can be formed when the react time is less than 10 h. With the increase of hydrothermal time, SnO 2 nanoparticles will self-assemble into SnO 2 nanosheets and Ag nanoparticles decorated SnO 2 nanosheets were obtained. When evaluated as catalyst, the obtained Ag-decorated SnO 2 microsphere prepared for 36 h exhibited excellent catalytic performance with normalized rate constant (κ nor ) of 6.20 min -1 g -1 L, which is much better than that of some previous reported catalysts. Moreover, this Ag-decorated SnO 2 microsphere demonstrates good reusability after the first five cycles. In addition, we speculate the formation mechanism of the hierarchical Ag-decorated SnO 2 microsphere and discussed the possible origin of the excellent catalytic activity.

MicroCub Subscale Aircraft

NASA Image and Video Library

2018-01-18

The MicroCub is the newest addition to NASA Armstrong's fleet of subscale research aircraft. The aircraft is a modified a Bill Hempel 60-percent-scale super cub, designed with a 21-foot wingspan, a Piccolo Autopilot guidance system and a JetCat SPT-15 Turboprop.

Optical absorption and photoluminescence study of nanocrystalline Zn0.92M0.08O (M: Li & Gd)

NASA Astrophysics Data System (ADS)

Punia, Khushboo; Lal, Ganesh; Kumar, Sudhish

2018-05-01

Nanocrystalline samples of Zn0.92Li0.08O and Zn0.92Gd0.08O have been synthesized using citrate sol-gel route without post synthesis annealing and characterized using powder X-ray diffraction (XRD), UV-Vis-NIR and Photoluminescence spectroscopic measurements. Analysis of XRD pattern and PL spectra revealed single phase formation of the nanocrystalline Zn0.92Li0.08O and Zn0.92Gd0.08O in the wurtzite type hexagonal structure with intrinsic crystal and surface defects. UV-Vis-NIR optical absorption measurements show that the maximum photo absorption occurs below 600nm in the UV& visible band. The estimated values of band gap energy were found to be 2.53eV and 2.73eV for Zn0.92Li0.08O and Zn0.92Gd0.08O respectively. The photoluminescence spectra excited at the wavelength 325nm displays two broad peaks in the UV and visible bands centered at ˜416 nm & ˜602 nm for Zn0.92Gd0.08O and ˜406nm & ˜598nm for Zn0.92Li0.08O. Both Gd and Li doping in ZnO leads to considerable decrease in the optical band gap energy and red shifting of the UV emission band towards the visible band.

Three-dimensional SnO2@TiO2 double-shell nanotubes on carbon cloth as a flexible anode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Haifeng; Ren, Weina; Cheng, Chuanwei

2015-07-01

In this study, three-dimensional SnO2@TiO2 double-shell nanotubes on carbon cloth are synthesized by a combination of the hydrothermal method for ZnO nanorods and a subsequent SnO2 and TiO2 thin film coating with atomic layer deposition (ALD). The as-prepared SnO2@TiO2 double-shell nanotubes are further tested as a flexible anode for Li ion batteries. The SnO2@TiO2 double-shell nanotubes/carbon cloth electrode exhibited a high initial discharge capacity (e.g. 778.8 mA h g-1 at a high current density of 780 mA g-1) and good cycling performance, which could be attributed to the 3D double-layer nanotube structure. The interior space of the stable TiO2 hollow tube can accommodate the large internal stress caused by volume expansion of SnO2 and protect SnO2 from pulverization and exfoliation.

Rapid synthesis of barium titanate microcubes using composite-hydroxides-mediated avenue

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Xi; Ouyang, Jing, E-mail: jingouyang@csu.edu.cn; Jin, Jiao

2014-04-01

Highlights: • Barium titanate oxides microcubes can be synthesized within 1 min. • Composite-hydroxides-mediated strategy provided a possible large scale production. • BST obtained in the strategy showed fairly good crystallinity and tetragonality. - Abstract: This paper reports the rapid synthesis of barium titanate (BaTiO{sub 3}, BTO) microcubes via composite-hydroxides-mediated reaction within 1 min. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrum (EDS) results confirmed both cubic and tetragonal lattices in the sample and the uniform microcubes with an average size of 1 μm. Ultraviolet–visible (UV–vis) spectrum indicated that the band gap of the BTO powder wasmore » 3.05 eV. Ferroelectric polarization vs. electric field (P–E) tests showed that the ferroelectric domains had formed in the as-synthesized BTO microcubes and sintered ceramics. BTO ceramics sintered at 1100 °C for 3 h showed fairly good tetragonality and possessed a maximum polarization of 0.21 μC/cm{sup 2}, indicating that the sintering temperature for the BTO powders prepared via this method was relatively low. The process and equipment reported herein provided a potential method for the rapid synthesis of titanate based perovskites.« less

Structural, Optical, and Photocatalytic Properties of Quasi-One-Dimensional Nanocrystalline ZnO, ZnOC:nC Composites, and C-doped ZnO

NASA Astrophysics Data System (ADS)

Shalaeva, E. V.; Gyrdasova, O. I.; Krasilnikov, V. N.; Melkozerova, M. A.; Baklanova, I. V.; Buldakova, L. Yu.

Various thermolysis rotes of zinc glicolate complexes are considered for the synthesis of quasi-one-dimensional nanostructured aggregates ZnO and Zn-O-C used as photocatalysts. Structural features of quasi-one-dimensional aggregates Zn-O-C and ZnO are investigated in detail. Transmission electron microscopy, Raman spectroscopy, and electron paramagnetic resonance spectroscopy methods demonstrate that the aggregates Zn-O-C have either composite structure (ZnO crystallites in amorphous carbon matrix) or a C-doped ZnO single-phase structure depending on heat treatment conditions, and that all the aggregates exhibit as a rule a tubular morphology, a nanocrystalline structure with a high specific surface area, and a high concentration of singly charged oxygen vacancies. The mechanism of the nanocrystalline structure formation is discussed and the effect of thermolysis condition on the formation of the textured structure of aggregates is investigated. The results of examination of the photocatalytic and optical absorption properties of the synthesized aggregates are presented. The photocatalytic activity for the hydroquinone oxidation reaction under ultraviolet and visible light increases in the series: the reference ZnO powder, quasi-one-dimensional ZnO, quasi-one-dimensional aggregates C-doped ZnO, and this tendency correlates with the reduction of the optical gap width. As a result of our studies, we have arrived at an important conclusion that thermal treatment of ZnO:nC composites allows a C-doped ZnO with high catalytic activity. This increasing photoactivity of C-doped ZnO aggregates is attributed to the optimal specific surface area and electron-energy spectrum restructuring to be produced owing to the presence of singly charged oxygen vacancies and carbon dissolved in the ZnO lattice.

Multiple electron injection dynamics in linearly-linked two dye co-sensitized nanocrystalline metal oxide electrodes for dye-sensitized solar cells.

PubMed

Shen, Qing; Ogomi, Yuhei; Park, Byung-wook; Inoue, Takafumi; Pandey, Shyam S; Miyamoto, Akari; Fujita, Shinsuke; Katayama, Kenji; Toyoda, Taro; Hayase, Shuzi

2012-04-07

Understanding the electron transfer dynamics at the interface between dye sensitizer and semiconductor nanoparticle is very important for both a fundamental study and development of dye-sensitized solar cells (DSCs), which are a potential candidate for next generation solar cells. In this study, we have characterized the ultrafast photoexcited electron dynamics in a newly produced linearly-linked two dye co-sensitized solar cell using both a transient absorption (TA) and an improved transient grating (TG) technique, in which tin(IV) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NcSn) and cis-diisothiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II) bis(tetrabutylammonium) (N719) are molecularly and linearly linked and are bonded to the surface of a nanocrystalline tin dioxide (SnO(2)) electrode by a metal-O-metal linkage (i.e. SnO(2)-NcSn-N719). By comparing the TA and TG kinetics of NcSn, N719, and hybrid NcSn-N719 molecules adsorbed onto both of the SnO(2) and zirconium dioxide (ZrO(2)) nanocrystalline films, the forward and backward electron transfer dynamics in SnO(2)-NcSn-N719 were clarified. We found that there are two pathways for electron injection from the linearly-linked two dye molecules (NcSn-N719) to SnO(2). The first is a stepwise electron injection, in which photoexcited electrons first transfer from N719 to NcSn with a transfer time of 0.95 ps and then transfer from NcSn to the conduction band (CB) of SnO(2) with two timescales of 1.6 ps and 4.2 ps. The second is direct photoexcited electron transfer from N719 to the CB of SnO(2) with a timescale of 20-30 ps. On the other hand, back electron transfer from SnO(2) to NcSn is on a timescale of about 2 ns, which is about three orders of magnitude slower compared to the forward electron transfer from NcSn to SnO(2). The back electron transfer from NcSn to N719 is on a timescale of about 40 ps, which is about one order slower compared to the forward electron transfer from N719 to Nc

Enhanced luminescence in Eu-doped ZnO nanocrystalline films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Keigo, E-mail: ksuzuki@murata.com; Murayama, Koji; Tanaka, Nobuhiko

We found an enhancement of Eu{sup 3+} emissions in Eu-doped ZnO nanocrystalline films fabricated by microemulsion method. The Eu{sup 3+} emission intensities were increased by reducing annealing temperatures from 633 K to 533 K. One possible explanation for this phenomenon is that the size reduction enhances the energy transfer from ZnO nanoparticles to Eu{sup 3+} ions. Also, the shift of the charge-transfer band into the low-energy side of the absorption edge is found to be crucial, which seems to expedite the energy transfer from O atoms to Eu{sup 3+} ions. These findings will be useful for the material design of Eu-doped ZnOmore » phosphors.« less

Calcination Method Synthesis of SnO2/g-C3N4 Composites for a High-Performance Ethanol Gas Sensing Application

PubMed Central

Cao, Jianliang; Qin, Cong; Wang, Yan; Zhang, Bo; Gong, Yuxiao; Zhang, Huoli; Sun, Guang; Bala, Hari; Zhang, Zhanying

2017-01-01

The SnO2/g-C3N4 composites were synthesized via a facile calcination method by using SnCl4·5H2O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), the field-emission scanning electron microscopy and transmission electron microscopy (SEM and TEM), energy dispersive spectrometry (EDS), thermal gravity and differential thermal analysis (TG-DTA), and N2-sorption. The analysis results indicated that the as-synthesized samples possess the two dimensional structure. Additionally, the SnO2 nanoparticles were highly dispersed on the surface of the g-C3N4nanosheets. The gas-sensing performance of the as-synthesized composites for different gases was tested. Moreover, the composite with 7 wt % g-C3N4 content (SnO2/g-C3N4-7) SnO2/g-C3N4-7 exhibits an admirable gas-sensing property to ethanol, which possesses a higher response and better selectivity than that of the pure SnO2-based sensor. The high surface area of the SnO2/g-C3N4 composite and the good electronic characteristics of the two dimensional graphitic carbon nitride are in favor of the elevated gas-sensing property. PMID:28468245

Identification of vacancy defect complexes in transparent semiconducting oxides ZnO, In2O3 and SnO2.

PubMed

Makkonen, Ilja; Korhonen, Esa; Prozheeva, Vera; Tuomisto, Filip

2016-06-08

Positron annihilation spectroscopy, when combined with supporting high-quality modeling of positron states and annihilation in matter, is a powerful tool for detailed defect identification of vacancy-type defects in semiconductors and oxides. Here we demonstrate that the Doppler broadening of the positron annihilation radiation is a very sensitive means for observing the oxygen environment around cation vacancies, the main open-volume defects trapping positrons in measurements made for transparent semiconducting oxides. Changes in the positron annihilation signal due to external manipulation such as irradiation and annealing can be correlated with the associated changes in the sizes of the detected vacancy clusters. Our examples for ZnO, In2O3 and SnO2 demonstrate that oxygen vacancies in oxides can be detected directly using positron annihilation spectroscopy when they are complexed with cation vacancies.

Identification of vacancy defect complexes in transparent semiconducting oxides ZnO, In2O3 and SnO2

NASA Astrophysics Data System (ADS)

Makkonen, Ilja; Korhonen, Esa; Prozheeva, Vera; Tuomisto, Filip

2016-06-01

Positron annihilation spectroscopy, when combined with supporting high-quality modeling of positron states and annihilation in matter, is a powerful tool for detailed defect identification of vacancy-type defects in semiconductors and oxides. Here we demonstrate that the Doppler broadening of the positron annihilation radiation is a very sensitive means for observing the oxygen environment around cation vacancies, the main open-volume defects trapping positrons in measurements made for transparent semiconducting oxides. Changes in the positron annihilation signal due to external manipulation such as irradiation and annealing can be correlated with the associated changes in the sizes of the detected vacancy clusters. Our examples for ZnO, In2O3 and SnO2 demonstrate that oxygen vacancies in oxides can be detected directly using positron annihilation spectroscopy when they are complexed with cation vacancies.

Synthesis and characterization of binary ZnO-SnO2 (ZTO) thin films by e-beam evaporation technique

NASA Astrophysics Data System (ADS)

Bibi, Shagufta; Shah, A.; Mahmood, Arshad; Ali, Zahid; Raza, Qaisar; Aziz, Uzma; Haneef; Waheed, Abdul; Shah, Ziaullah

2018-04-01

The binary ZnO-SnO2 (ZTO) thin films with varying SnO2 concentrations (5, 10, 15, and 20 wt%) were grown on glass substrate by e-beam evaporation technique. The prepared ZTO films were annealed at 400 °C in air. These films were then characterized to investigate their structural, optical, and electrical properties as a function of SnO2 concentration. XRD analysis reveals that the crystallinity of the film decreases with the addition of SnO2 and it transforms to an amorphous structure at a composition of 40% SnO2 and 60% ZnO. Morphology of the films was examined by atomic force microscopy which points out that surface roughness of the films decreases with the increasing of SnO2 in the film. Optical properties such as optical transparency, band-gap energy, and optical constants of these films were examined by spectrophotometer and spectroscopic Ellipsometer. It was observed that the average optical transmission of mixed films improves with incorporation of SnO2. In addition, the band-gap energy of the films was determined to be in the range of 3.37-3.7 eV. Furthermore, it was found that the optical constants (n and k) decrease with the addition of SnO2. Similarly, it is observed that the electrical resistivity increases nonlinearly with the increase in SnO2 in ZnO-SnO2 thin films. However, it is noteworthy that the highest figure of merit (FOM) value, i.e., 55.87 × 10-5 Ω-1, is obtained for ZnO-SnO2 (ZTO) thin film with 40 wt% of SnO2 composition. Here, we suggest that ZnO-SnO2 (ZTO) thin film with composition of 60:40 wt% can be used as an efficient TCO film due to the improved transmission, and reduced RMS value and highest FOM value.

A simple structure of Cu2ZnSnS4/CdS solar cells prepared by sputtering

NASA Astrophysics Data System (ADS)

Li, Zhishan; Wang, Shurong; Ma, Xun; Yang, Min; Jiang, Zhi; Liu, Tao; Lu, Yilei; Liu, Sijia

2017-12-01

In this work, Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by annealing of sputtered ZnS/Sn/CuS precursors at 580 ℃ for 15 min. As a try, the CZTS solar cells were fabricated using simple structure of Mo-coated SLG/CZTS/CdS/Al and traditional structure of Mo-coated SLG/CZTS/CdS/i-ZnO/In2O3:SnO2 (ITO)/Al, respectively. The results show that the CZTS device with simple structure can achieve same level of the open circuit voltage (Voc) compared with that of traditional structure. In addition, the power conversion efficiency of 2.95% and 3.59% were obtained with simple structure and traditional structure, respectively. The CZTS solar cell with simple structure provides a promising way and an easy process to prepare high-performance CZTS thin film solar cells which is available to large-scale industrial production in the future.

Novel development of nanocrystalline kesterite Cu2ZnSnS4 thin film with high photocatalytic activity under visible light illumination

NASA Astrophysics Data System (ADS)

Apostolopoulou, Andigoni; Mahajan, Sandip; Sharma, Ramphal; Stathatos, Elias

2018-01-01

Cu2ZnSnS4 (CZTS) represents a promising p-type direct band gap semiconductor with large absorption coefficient in the visible region of solar light. In the present study, a kesterite CZTS nanocrystalline film, with high purity, was successfully synthesized via the combination of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) technique. The morphology and structural properties of the CZTS films were characterized by FE-SEM microscopy, porosimetry in terms of Brunauer-Emmett-Teller (BET) technique, X-ray diffraction and Raman spectroscopy. The as-prepared films under mild heat treatment at 250 °C in the presence of sulfur atmosphere exhibited fine nanostructure with 35 nm average particle size, high specific surface area of 53 m2/g and 9 nm pore diameter. The photocatalytic activity of the films was examined to the degradation of Basic Blue 41 (BB-41) and Acid Orange 8 (AO-8) organic azo dyes under visible light irradiation, demonstrating 97.5% and 70% discoloration for BB-41 and AO-8 respectively. Reusability of the CZTS films was also tested proving good stability over several repetitions. The reduction of photocatalyst's efficiency after three successive repetitions didn't exceed 5.6% and 8.5% for BB-41 and AO-8 respectively.

Effect of milling atmosphere on structural and magnetic properties of Ni-Zn ferrite nanocrystalline

NASA Astrophysics Data System (ADS)

Hajalilou, Abdollah; Hashim, Mansor; Ebrahimi-Kahrizsangi, Reza; Masoudi Mohamad, Taghi

2015-04-01

Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres (argon, air, and oxygen), milling time (from 0 to 30 h) and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600 °C for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated. Project supported by the University Putra Malaysia Graduate Research Fellowship Section.

Characterization of core/shell structures based on CdTe and GaAs nanocrystalline layers deposited on SnO2 microwires

NASA Astrophysics Data System (ADS)

Ghimpu, L.; Ursaki, V. V.; Pantazi, A.; Mesterca, R.; Brâncoveanu, O.; Shree, Sindu; Adelung, R.; Tiginyanu, I. M.; Enachescu, M.

2018-04-01

We report the fabrication and characterization of SnO2/CdTe and SnO2/GaAs core/shell microstructures. CdTe or GaAs shell layers were deposited by radio-frequency (RF) magnetron sputtering on core SnO2 microwires synthesized by a flame-based thermal oxidation method. The produced structures were characterized by scanning electron microscopy (SEM), high-resolution scanning transmission electron microscope (HR-STEM), X-ray diffraction (XRD), Raman scattering and FTIR spectroscopy. It was found that the SnO2 core is of the rutile type, while the shells are composed of CdTe or GaAs nanocrystallites of zincblende structure with the dimensions of crystallites in the range of 10-20 nm. The Raman scattering investigations demonstrated that the quality of the porous nanostructured shell is improved by annealing at temperatures of 420-450 °C. The prospects of implementing these microstructures in intrinsic type fiber optic sensors are discussed.

Correlation between emission property and concentration of Sn2+ center in the SnO-ZnO-P2O5 glass.

PubMed

Masai, Hirokazu; Tanimoto, Toshiro; Fujiwara, Takumi; Matsumoto, Syuji; Tokuda, Yomei; Yoko, Toshinobu

2012-12-03

The authors report on the correlation between the photoluminescence (PL) property and the SnO amount in SnO-ZnO-P2O5 (SZP) glass. In the PL excitation (PLE) spectra of the SZP glass containing Sn2+ emission center, two S1 states, one of which is strongly affected by SnO amount, are assumed to exist. The PLE band closely correlates with the optical band edge originating from Sn2+ species, and they both largely red-shifts with increasing amount of SnO. The emission decay time of the SZP glass decreased with increasing amount of SnO and the internal quantum efficiencies of the SZP glasses containing 1~5 mol% of SnO are comparable to that of MgWO4. It is expected that the composition-dependent S1 state (the lower energy excitation band) governs the quantum efficiency of the SZP glasses.

Preparation, characterization and nonlinear absorption studies of cuprous oxide nanoclusters, micro-cubes and micro-particles

NASA Astrophysics Data System (ADS)

Sekhar, H.; Narayana Rao, D.

2012-07-01

Cuprous oxide nanoclusters, micro-cubes and micro-particles were successfully synthesized by reducing copper(II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction and FTIR studies revealed that the formation of pure single-phase cubic. Raman and EPR spectral studies show the presence of CuO in as-synthesized powders of Cu2O. Transmission electron microscopy and field emission scanning electron microscopy data revealed that the morphology evolves from nanoclusters to micro-cubes and micro-particles by increasing the concentration of NaOH. Linear optical measurements show absorption peak maximum shifts towards red with changing morphology from nanoclusters to micro-cubes and micro-particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm 6 ns laser pulses. Samples-exhibited both saturable as well as reverse saturable absorption. Due to confinement effects (enhanced band gap), we observed enhanced nonlinear absorption coefficient (β) in the case of nanoclusters compared to their micro-cubes and micro-particles.

Characterization of SnO2 Film with Al-Zn Doping Using Sol-Gel Dip Coating Techniques

NASA Astrophysics Data System (ADS)

Doyan, A.; Susilawati; Ikraman, N.; Taufik, M.

2018-04-01

Sn1-2x AlxZnxO2 film has been developed using sol-gel dip coating technique. The materials SnCl2.2H2O, AlCl3 and ZnCl2 dissolved in water and ethanol with 5:95 volume ratio. Variations dopant concentration x = 0.000, 0.005, 0.0025, and 0.050. The film was grown with sol concentration 0.4 M, the withdrawal speed of 12 cm/min and sintering at 600 °C for 30 minutes. The characteristics Sn1-2x AlxZnxO2 films with various doping concentration phase were characterized by XRD. The morphological characteristics and the composition of the constituent elements of the film were characterized by SEM-EDX. The characteristics of the shape, structure, and size of the particles were characterized by TEM. The XRD results show that all films have a tetragonal SnO2 rutile phase without any secondary phase with an average particle size in the range 5.14 – 2.09 nm. The SEM results show that the film grown has a smooth morphology with a striped texture (x = 0.00), and there is a crack (x = 0.050). The EDX results show that the composition and distribution of the constituent elements of the film are uniformly distributed. TEM results show that the particle films has tetragonal rutile structure, orthorhombic and amorphous with a spherical shape.

Novel microwave-assisted synthesis of porous g-C3N4/SnO2 nanocomposite for solar water-splitting

NASA Astrophysics Data System (ADS)

Seza, A.; Soleimani, F.; Naseri, N.; Soltaninejad, M.; Montazeri, S. M.; Sadrnezhaad, S. K.; Mohammadi, M. R.; Moghadam, H. Asgari; Forouzandeh, M.; Amin, M. H.

2018-05-01

Highly porous nanocomposites of graphitic-carbon nitride and tin oxide (g-C3N4/SnO2) were prepared through simple pyrolysis of urea molecules under microwave irradiation. The initial amount of tin was varied in order to investigate the effect of SnO2 content on preparation and properties of the composites. The synthesized nanocomposites were well-characterized by XRD, FE-SEM, HR-TEM, BET, FTIR, XPS, DRS, and PL. A homogeneous distribution of SnO2 nanoparticles with the size of less than 10 nm on the porous C3N4 sheets could be obtained, suggesting that in-situ synthesis of SnO2 nanoparticles was responsible for the formation of g-C3N4. The process likely occurred by the aid of the large amounts of OH groups formed on the surfaces of SnO2 nanoparticles during the polycondensation reactions of tin derivatives which could facilitate the pyrolysis of urea to carbon nitride. The porous nanocomposite prepared with initial tin amount of 0.175 g had high specific surface area of 195 m2 g-1 which showed high efficiency photoelectrochemical water-splitting ability. A maximum photocurrent density of 33 μA cm-2 was achieved at an applied potential of 0.5 V when testing this nanocomposite as photo-anode in water-splitting reactions under simulated visible light irradiation, introducing it as a promising visible light photoactive material.

Dendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteries.

PubMed

Liu, Zhen; Cui, Tong; Pulletikurthi, Giridhar; Lahiri, Abhishek; Carstens, Timo; Olschewski, Mark; Endres, Frank

2016-02-18

Metallic zinc is a promising anode material for rechargeable Zn-based batteries. However, the dendritic growth of zinc has prevented practical applications. Herein it is demonstrated that dendrite-free zinc deposits with a nanocrystalline structure can be obtained by using nickel triflate as an additive in a zinc triflate containing ionic liquid. The formation of a thin layer of Zn-Ni alloy (η- and γ-phases) on the surface and in the initial stages of deposition along with the formation of an interfacial layer on the electrode strongly affect the nucleation and growth of zinc. A well-defined and uniform nanocrystalline zinc deposit with particle sizes of about 25 nm was obtained in the presence of Ni(II) . Further, it is shown that the nanocrystalline Zn exhibits a high cycling stability even after 50 deposition/stripping cycles. This strategy of introducing an inorganic metal salt in ionic liquid electrolytes can be considered as an efficient way to obtain dendrite-free zinc. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SU-E-T-172: Characterization of TLD-100 (LiF:Mg,Ti) Microcube Energy Response in a Cylindrical Chamber Phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, V; Hammer, C; Kunugi, K

Purpose: To characterize the energy response of TLD-100 microcubes inside a Virtual Water chamber phantom. Methods: Four TLD microcubes were placed inside a water-proof Virtual Water (VW) chamber phantom and irradiated to a known dose on a Varian linac in a 1D water tank. These chamber phantoms were then replaced by TLD-100 chips inside a separate VW paddle and irradiated to the same dose. Each energy response reading was calculated as light output per unit dose in nC/cGy and normalized to a calibration set irradiated to the same dose in 60Co. The differences in response between the TLD chips andmore » microcubes were then analyzed. Results: Across all energies, the average microcube response was less sensitive to energy than the average chip response with both falling consistently within 2.8% of previously established values in the literature Conclusion: TLD microcubes showed a lower average sensitivity to energy than their TLD chip counterparts. The use of TLD-100 microcubes inside the chamber phantom was validated against TLD-100 chips inside of VW paddles.« less

Investigation of the structure and stability of SnO2 nanocrystal and its surface-bound water

NASA Astrophysics Data System (ADS)

Wang, H.; Wesolowski, D. J.; Proffen, T. E.; Kolesnikov, A. I.; Vlcek, L.; Wang, W.; Feygenson, M.; Sofo, J. O.; Anovitz, L.

2012-12-01

Driven partly by a myriad use of engineered metal oxide nanoparticles, understanding their stabilities and interactions with environmental matrix during and after applications are desired. SnO2 (cassiterite) is one of the frequently used oxides in solid-state gas sensors and oxidation catalysts. A close relationship between the gas sensitivity and catalysis of oxides with their surface chemistry ensures continuous interests in the study of SnO2-water interfacial complexity (unavoidable "contamination" in which water can potentially participate in reactions and change SnO2 conductivity). Such information is important, as the existence of hydration layers on the surface of SnO2 nanoparticles not only play a critical role in stabilizing the nanoparticle but also affect its selectivity/sensitivity, as a nanosensor. SnO2 nanoparticles (2-5 nm) synthesized by a wet chemical route are dominated by {110} faces and are capped with H2O or D2O water molecules (after purification), depending on isotopic composition of water used for syntheses. When water is in direct contact with terminal Sn and O atoms, there is a controversial argument as to whether or not dissociative adsorption occurs (i.e., formation of hydroxyl groups). Although theoretical studies point toward a tendency for dissociative configuration in the direct contact layer, experimental studies have not unambiguously confirmed this conclusion. We present combined investigations using neutron total scattering (NPDF at the NOMAD beamline, SNS) and inelastic neutron scattering (INS at the SEQUOIA beamline, SNS) techniques as static and dynamic probes to reveal structure and dynamics of water and SnO2 nanocrystalline stability upon dehydration. The NPDF results (measured with deuterated samples) suggest layered water configurations with G(r) signals dominated by O-D bonds at 0.98 Å, and the second hydration layer that gives a broad peak at 2.5-4 Å. There is no evidence of a third hydration layer at 5-7 Å as shown

Ultrasonic-assisted pyrolyzation fabrication of reduced SnO2–x /g-C3N4 heterojunctions: Enhance photoelectrochemical and photocatalytic activity under visible LED light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kai; Zeng, Xiaoqiao; Gao, Shanmin

Novel SnO 2–x/g-C 3N 4 heterojunction nanocomposites composed of reduced SnO 2–x nanoparticles and exfoliated g-C 3N 4 nanosheets were prepared by a convenient one-step pyrolysis method. The structural, morphological, and optical properties of the as-prepared nanocomposites were characterized in detail, indicating that the aggregation of g-C 3N 4 nanosheets was prevented by small, well-dispersed SnO 2–x nanoparticles. The ultraviolet–visible spectroscopy absorption bands of the nanocomposites were shifted to a longer wavelength region than those exhibited by pure SnO 2 or g-C 3N 4. The charge transfer and recombination processes occurring in the nanocomposites were investigated using linear scan voltammetrymore » and electrochemical impedance spectroscopy. Under 30-W visible-light-emitting diode irradiation, the heterojunction containing 27.4 wt.% SnO 2–x exhibited the highest photocurrent density of 0.0468 mA·cm–2, which is 33.43 and 5.64 times larger than that of pure SnO 2 and g-C 3N 4, respectively. The photocatalytic activity of the heterojunction material was investigated by degrading rhodamine B under irradiation from the same light source. Kinetic study revealed a promising degradation rate constant of 0.0226 min-1 for the heterojunction containing 27.4 wt.% SnO 2–x, which is 32.28 and 5.79 times higher than that of pure SnO 2 and g-C 3N 4, respectively. The enhanced photoelectrochemical and photocatalytic performances of the nanocomposite may be due to its appropriate SnO 2–x content and the compact structure of the junction between the SnO 2–x nanoparticles and the g-C 3N 4 nanosheets, which inhibits the recombination of photogenerated electrons and holes.« less

SnoN Stabilizes the SMAD3/SMAD4 Protein Complex

PubMed Central

Walldén, Karin; Nyman, Tomas; Hällberg, B. Martin

2017-01-01

TGF-β signaling regulates cellular processes such as proliferation, differentiation and apoptosis through activation of SMAD transcription factors that are in turn modulated by members of the Ski-SnoN family. In this process, Ski has been shown to negatively modulate TGF-β signaling by disrupting active R-SMAD/Co-SMAD heteromers. Here, we show that the related regulator SnoN forms a stable complex with the R-SMAD (SMAD3) and the Co-SMAD (SMAD4). To rationalize this stabilization at the molecular level, we determined the crystal structure of a complex between the SAND domain of SnoN and the MH2-domain of SMAD4. This structure shows a binding mode that is compatible with simultaneous coordination of R-SMADs. Our results show that SnoN, and SMAD heteromers can form a joint structural core for the binding of other transcription modulators. The results are of fundamental importance for our understanding of the molecular mechanisms behind the modulation of TGF-β signaling. PMID:28397834

SnoN Stabilizes the SMAD3/SMAD4 Protein Complex.

PubMed

Walldén, Karin; Nyman, Tomas; Hällberg, B Martin

2017-04-11

TGF-β signaling regulates cellular processes such as proliferation, differentiation and apoptosis through activation of SMAD transcription factors that are in turn modulated by members of the Ski-SnoN family. In this process, Ski has been shown to negatively modulate TGF-β signaling by disrupting active R-SMAD/Co-SMAD heteromers. Here, we show that the related regulator SnoN forms a stable complex with the R-SMAD (SMAD3) and the Co-SMAD (SMAD4). To rationalize this stabilization at the molecular level, we determined the crystal structure of a complex between the SAND domain of SnoN and the MH2-domain of SMAD4. This structure shows a binding mode that is compatible with simultaneous coordination of R-SMADs. Our results show that SnoN, and SMAD heteromers can form a joint structural core for the binding of other transcription modulators. The results are of fundamental importance for our understanding of the molecular mechanisms behind the modulation of TGF-β signaling.

Hollow SnO2@Co3O4 core-shell spheres encapsulated in three-dimensional graphene foams for high performance supercapacitors and lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhao, Bo; Huang, Sheng-Yun; Wang, Tao; Zhang, Kai; Yuen, Matthew M. F.; Xu, Jian-Bin; Fu, Xian-Zhu; Sun, Rong; Wong, Ching-Ping

2015-12-01

Hollow SnO2@Co3O4 spheres are fabricated using 300 nm spherical SiO2 particles as template. Then three-dimensional graphene foams encapsulated hollow SnO2@Co3O4 spheres are successfully obtained through self-assembly in hydrothermal process from graphene oxide nanosheets and metal oxide hollow spheres. The three-dimensional graphene foams encapsulated architectures could greatly improve the capacity, cycling stability and rate capability of hollow SnO2@Co3O4 spheres electrodes due to the highly conductive networks and flexible buffering matrix. The three-dimensional graphene foams encapsulated hollow SnO2@Co3O4 spheres are promising electrode materials for supercapacitors and lithium-ion batteries.

Enhanced photovoltaic performance of dye sensitized solar cell using SnO2 nanoflowers

NASA Astrophysics Data System (ADS)

Arote, Sandeep A.; Tabhane, Vilas A.; Pathan, Habib M.

2018-01-01

The study highlighted enhanced performance of SnO2 based DSSC using photoanode with nanostructured morphology. The simple organic surfactant free hydrothermal synthesis method was used for preparation of SnO2 nanoflowers for dye sensitized solar cell (DSSC) application. The hydrothermal reaction time was varied to obtain different SnO2 nanostructures. The hydrothermal reaction time showed considerable effect on optical and structural properties of the prepared samples. The results indicated that the prepared samples were pure rutile SnO2. The band gap of prepared samples was greater than bulk SnO2 and varied from 3.64 to 3.81 eV with increase in hydrothermal reaction time. With increase in reaction time from 4 to 24 h, the microstructure of SnO2 changed from agglomerated nanoparticles to nanopetals and finally to self-assembled nanoflowers. Flower-like SnO2 nanostructures showed size around 300-700 nm, and composed of large numbers of 3 dimensional petals connected with each other forming 3D nanoflowers by self-assembly. Consequently, the DSSC with flower-like SnO2 nanostructures exhibited good photovoltaic performance with Voc, Jsc and η about 0.43 V, 4.36 mA/cm2 and 1.11%, respectively.

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

SnO 2 nanowires decorated with forsythia-like TiO 2 for photoenergy conversion

DOE PAGES

Park, Ik Jae; Park, Sangbaek; Kim, Dong Hoe; ...

2017-05-17

Here, we report forsythia-like TiO 2-decorated SnO 2 nanowires on fluorine-doped SnO 2 electrode as a photoelectrode of dye-sensitized solar cells. When SnO 2 nanowires grown via vapor-liquid-solid reaction were soaked in TiCl 4 solution, leaf-shaped rutile TiO 2 was grown onto the surface of the nanowires. The TiO 2 decoration increases the short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) of dye-sensitized solar cells. Further, electron lifetime increased by employing an atomic-layer-deposited TiO 2 nanoshell between the TiO 2 leaves and the SnO 2 nanowire, due to preventing charge recombination at the nanowire/electrolytemore » interface.« less

Dynamic creation and evolution of gradient nanostructure in single-crystal metallic microcubes

NASA Astrophysics Data System (ADS)

Thevamaran, Ramathasan; Lawal, Olawale; Yazdi, Sadegh; Jeon, Seog-Jin; Lee, Jae-Hwang; Thomas, Edwin L.

2016-10-01

We demonstrate the dynamic creation and subsequent static evolution of extreme gradient nanograined structures in initially near-defect-free single-crystal silver microcubes. Extreme nanostructural transformations are imposed by high strain rates, strain gradients, and recrystallization in high-velocity impacts of the microcubes against an impenetrable substrate. We synthesized the silver microcubes in a bottom-up seed-growth process and use an advanced laser-induced projectile impact testing apparatus to selectively launch them at supersonic velocities (~400 meters per second). Our study provides new insights into the fundamental deformation mechanisms and the effects of crystal and sample-shape symmetries resulting from high-velocity impacts. The nanostructural transformations produced in our experiments show promising pathways to developing gradient nanograined metals for engineering applications requiring both high strength and high toughness—for example, in structural components of aircraft and spacecraft.

Preparation of Zn(BH4)2 and diborane and hydrogen release properties of Zn(BH4)2+xMgH2 (x=1, 5, 10, and 15)

NASA Astrophysics Data System (ADS)

Kwak, Young Jun; Kwon, Sung Nam; Song, Myoung Youp

2015-09-01

Zn(BH4)2 was prepared by milling ZnCl2 and NaBH4 in a planetary ball mill under Ar atmosphere, and Zn(BH4)2+xMgH2 (x=1, 5, 10, and 15) samples were prepared. Diborane (B2H6) and hydrogen release characteristics of the Zn(BH4)2 and Zn(BH4)2+xMgH2 samples were studied. The samples synthesized by milling ZnCl2 and NaBH4 contained Zn(BH4)2 and NaCl, together with small amounts of ZnCl2 and NaBH4. We designated these samples as Zn(BH4)2(+NaCl). The weight loss up to 400 °C of the Zn(BH4)2(+NaCl) sample synthesized by milling 4 h was 11.2 wt%. FT-IR analysis showed that Zn(BH4)2 was formed in the Zn(BH4)2(+NaCl) samples. MgH2 was also milled in a planetary ball mill, and mixed with the Zn(BH4)2(+NaCl) synthesized by milling for 4 h in a mortar and pestle. The weight loss up to 400 °C of Zn(BH4)2(+NaCl)+MgH2 was 8.2 wt%, corresponding to the weight % of diborane and hydrogen released from the Zn(BH4)2(+NaCl)+MgH2 sample, with respect to the sample weight. DTA results of Zn(BH4)2(+NaCl)+xMgH2 showed that the decomposition peak of Zn(BH4)2 was at about 61 °C, and that of MgH2 was at about 370-389 °C.

Effect of Zn addition on structural, magnetic properties, antistructural modeling of Co1-xZnxFe2O4 nano ferrite

NASA Astrophysics Data System (ADS)

Raghuvanshi, S.; Kane, S. N.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

Effect of Zn addition on cationic distribution, structural properties, magnetic properties, antistructural modeling of nanocrystalline Co1-xZnxFe2O4 (0.08 ≤ x ≤ 0.56) ferrite is reported. XRD confirms the formation of single phase cubic spinel nano ferrites with average grain diameter ranging between 41.2 - 54.9 nm. Coercivity (Hc), anisotropy constant (K1) decreases with Zn addition, but experimental, theoretical saturation magnetization (Ms, Ms(t)) increases upto x = 0.32, then decreases, attributed to the breaking of collinear ferrimagnetic phase. Variation of magnetic properties is correlated with cationic distribution. A new antistructural modeling for describing active surface centers is discussed to explain change in concentration of donor's active centers Zn'B, Co'B, acceptor's active centers Fe*A are explained.

Nano SnO 2-Al 2O 3 mixed oxide and SnO 2-Al 2O 3-carbon composite oxides as new and novel electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Jayalakshmi, M.; Venugopal, N.; Raja, K. Phani; Rao, M. Mohan

New nano-materials like SnO 2-Al 2O 3 and SnO 2-Al 2O 3-carbon were synthesized by a single step hydrothermal method in searching for novel mixed oxides with high electrochemical double layer capacitance. A SnO 2-Al 2O 3-carbon sample was calcined at 600 °C and tested for its performance. The source of carbon was tetrapropyl ammonium hydroxide. The capacitive behavior of SnO 2 was compared to the performance of SnO 2-Al 2O 3, SnO 2-Al 2O 3-carbon and calcined SnO 2-Al 2O 3-carbon using the techniques of cyclic voltammetry, double potential step, chronopotentiometry and E-log I polarization. In 0.1 M NaCl solutions, SnO 2-Al 2O 3 gave the best performance with a value of 119 Fg -1 and cycled 1000 times. The nano-material mixed oxides were characterized by TEM, XRD, ICP-AES and SEM-EDAX.

SU-G-201-08: Energy Response of Thermoluminescent Microcube Dosimeters in Water for Kilovoltage X-Ray Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Maso, L; Lawless, M; Culberson, W

Purpose: To characterize the energy dependence for TLD-100 microcubes in water at kilovoltage energies. Methods: TLD-100 microcubes with dimensions of (1 × 1 × 1) mm{sup 3} were irradiated with kilovoltage x-rays in a custom-built thin-window liquid water phantom. The TLD-100 microcubes were held in Virtual Water™ probes and aligned at a 2 cm depth in water. Irradiations were performed using the M-series x-ray beams of energies ranging from 50-250 kVp and normalized to a {sup 60}Co beam located at the UWADCL. Simulations using the EGSnrc Monte Carlo Code System were performed to model the x-ray beams, the {sup 60}Comore » beam, the water phantom and the dosimeters in the phantom. The egs-chamber user code was used to tally the dose to the TLDs and the dose to water. The measurements and calculations were used to determine the intrinsic energy dependence, absorbed-dose energy dependence, and absorbed-dose sensitivity. These values were compared to TLD-100 chips with dimensions of (3.2 × 0.9 × 0.9) mm{sup 3}. Results: The measured TLD-100 microcube response per dose to water among all investigated x-ray energies had a maximum percent difference of 61% relative to {sup 60}Co. The simulated ratio of dose to water to the dose to TLD had a maximum percent difference of 29% relative to {sup 60}Co. The ratio of dose to TLD to the TLD output had a maximum percent difference of 13% relative to {sup 60}Co. The maximum percent difference for the absorbed-dose sensitivity was 15% more than the used value of 1.41. Conclusion: These results confirm that differences in beam quality have a significant effect on TLD response when irradiated in water. These results also indicated a difference in TLD-100 response between microcube and chip geometries. The intrinsic energy dependence and the absorbed-dose energy dependence deviated up to 10% between TLD-100 microcubes and chips.« less

Nature of Dielectric Properties, Electric Modulus and AC Electrical Conductivity of Nanocrystalline ZnIn2Se4 Thin Films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.

2018-02-01

The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.

Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O

PubMed Central

Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang

2014-01-01

The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl− and H2O around Zn2+. According to the solid–liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn2+ both in a tetra­hedral coordination with Cl− and in an octa­hedral environment defined by five water mol­ecules and one Cl− shared with the [ZnCl4]2− unit. Thus, these two different types of Zn2+ cations form isolated units with composition [Zn2Cl4(H2O)5] (penta­aqua-μ-chlorido-tri­chlorido­di­zinc). The trihydrate {hexa­aqua­zinc tetra­chlorido­zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn2+ cations, one of which is tetra­hedrally coordinated by four Cl− anions. The two other Zn2+ cations are each located on an inversion centre and are octa­hedrally surrounded by water mol­ecules. The [ZnCl4] tetra­hedra and [Zn(H2O)6] octa­hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa­aqua­zinc tetra­chlorido­zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa­hedral [Zn(H2O)6] and tetra­hedral [ZnCl4] units, as well as additional lattice water mol­ecules. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ZnCl4 tetra­hedra and water mol­ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures. PMID:25552980

Abundant defects and defect clusters in kesterite Cu2ZnSnS4 and Cu2ZnSnSe4

NASA Astrophysics Data System (ADS)

Chen, Shiyou; Wang, Lin-Wang; Walsh, Aron; Gong, Xin-Gao; Wei, Su-Huai

2013-03-01

Cu2ZnSnS4 and Cu2ZnSnSe4 are drawing intensive attention as the light-absorber materials in thin-film solar cells. A large variety of intrinsic defects can be formed in these quaternary semiconductors, which have important influence on their optical and electrical properties, and hence their photovoltaic performance. We will present our first-principles calculation study on a series of intrinsic defects and defect clusters in Cu2ZnSnS4 and Cu2ZnSnSe4, and discuss: (i) strong phase-competition between the kesterites and the coexisting secondary compounds; (ii) the dominant CuZn antisites and Cu vacancies which determine the intrinsic p-type conductivity, and their dependence on the elemental ratios; (iii) the high population of charge-compensated defect clusters (like VCu + ZnCu and 2CuZn + SnZn) and their contribution to non-stoichiometry ; (iv) the deep-level defects which act as recombination centers. Based on the calculation, we will explain the experimental observation that Cu poor and Zn rich conditions give the highest solar cell efficiency, as well as suggesting an efficiency limitation in Cu2ZnSn(S,Se)4 cells with high S composition. Supported by NSF of China, JCAP: a U.S. DOE Energy Innovation Hub, Royal Society of U.K. and EPSRC, and U.S. DOE.

Dynamic creation and evolution of gradient nanostructure in single-crystal metallic microcubes.

PubMed

Thevamaran, Ramathasan; Lawal, Olawale; Yazdi, Sadegh; Jeon, Seog-Jin; Lee, Jae-Hwang; Thomas, Edwin L

2016-10-21

We demonstrate the dynamic creation and subsequent static evolution of extreme gradient nanograined structures in initially near-defect-free single-crystal silver microcubes. Extreme nanostructural transformations are imposed by high strain rates, strain gradients, and recrystallization in high-velocity impacts of the microcubes against an impenetrable substrate. We synthesized the silver microcubes in a bottom-up seed-growth process and use an advanced laser-induced projectile impact testing apparatus to selectively launch them at supersonic velocities (~400 meters per second). Our study provides new insights into the fundamental deformation mechanisms and the effects of crystal and sample-shape symmetries resulting from high-velocity impacts. The nanostructural transformations produced in our experiments show promising pathways to developing gradient nanograined metals for engineering applications requiring both high strength and high toughness-for example, in structural components of aircraft and spacecraft. Copyright © 2016, American Association for the Advancement of Science.

Screen-printed SnO2/CNT quasi-solid-state gel-electrolyte supercapacitor

NASA Astrophysics Data System (ADS)

Kuok, Fei-Hong; Liao, Chen-Yu; Chen, Chieh-Wen; Hao, Yu-Chuan; Yu, Ing-Song; Chen, Jian-Zhang

2017-11-01

This study investigates a quasi-solid-state gel-electrolyte supercapacitor fabricated with nanoporous SnO2/CNT nanocomposite electrodes and a polyvinyl alcohol/sulfuric acid (PVA/H2SO4) gel electrolyte. First, pastes containing SnO2 nanoparticles, CNTs, ethyl cellulose, and terpineol are screen-printed onto carbon cloth. A tube furnace is then used for calcining the SnO2/CNT electrodes on carbon cloth. After furnace-calcination, the wettability of SnO2/CNT significantly improved; furthermore, the XPS analysis shows that number of C-O bond and oxygen content significantly decrease after furnace-calcination owing to the burnout of the ethyl cellulose by the furnace calcination processes. The furnace-calcined SnO2/CNT electrodes sandwich the PVA/H2SO4 gel electrolyte to form a supercapacitor. The fabricated supercapacitor exhibits an areal capacitance of 5.61 mF cm-2 when flat and 5.68 mF cm-2 under bending with a bending radius (R) of 1.0 cm. After a 1000 cycle stability test, the capacitance retention rates of the supercapacitor are 96% and 97% when flat and under bending (R  =  1.0 cm), respectively.

Time-Resolved Optical Emission Spectroscopy Diagnosis of CO2 Laser-Produced SnO2 Plasma

NASA Astrophysics Data System (ADS)

Lan, Hui; Wang, Xinbing; Zuo, Duluo

2016-09-01

The spectral emission and plasma parameters of SnO2 plasmas have been investigated. A planar ceramic SnO2 target was irradiated by a CO2 laser with a full width at half maximum of 80 ns. The temporal behavior of the specific emission lines from the SnO2 plasma was characterized. The intensities of Sn I and Sn II lines first increased, and then decreased with the delay time. The results also showed a faster decay of Sn I atoms than that of Sn II ionic species. The temporal evolutions of the SnO2 plasma parameters (electron temperature and density) were deduced. The measured temperature and density of SnO2 plasma are 4.38 eV to 0.5 eV and 11.38×1017 cm-3 to 1.1×1017 cm-3, for delay times between 0.1 μs and 2.2 μs. We also investigated the effect of the laser pulse energy on SnO2 plasma. supported by National Natural Science Foundation of China (No. 11304235) and the Director Fund of WNLO

Facile method for preparing superoleophobic surfaces with hierarchical microcubic/nanowire structures

NASA Astrophysics Data System (ADS)

Kwak, Wonshik; Hwang, Woonbong

2016-02-01

To facilitate the fabrication of superoleophobic surfaces having hierarchical microcubic/nanowire structures (HMNS), even for low surface tension liquids including octane (surface tension = 21.1 mN m-1), and to understand the influences of surface structures on the oleophobicity, we developed a convenient method to achieve superoleophobic surfaces on aluminum substrates using chemical acid etching, anodization and fluorination treatment. The liquid repellency of the structured surface was validated through observable experimental results the contact and sliding angle measurements. The etching condition required to ensure high surface roughness was established, and an optimal anodizing condition was determined, as a critical parameter in building the superoleophobicity. The microcubic structures formed by acid etching are essential for achieving the formation of the hierarchical structure, and therefore, the nanowire structures formed by anodization lead to an enhancement of the superoleophobicity for low surface tension liquids. Under optimized morphology by microcubic/nanowire structures with fluorination treatment, the contact angle over 150° and the sliding angle less than 10° are achieved even for octane.

On the 16O 6+ ion irradiation induced magnetic moment generation in ZnFe2O4 nano ferrite

NASA Astrophysics Data System (ADS)

Satalkar, M.; Kane, S. N.; Raghuvanshi, S.

2018-05-01

X-ray diffraction (XRD) was utilized to study the effect of 80 MeV 16O 6+ ion irradiation of the as-burnt ZnFe2O4 samples, prepared by sol-gel auto-combustion technique. The samples were irradiated at fluence: 1 × 1011, 1 × 1012, 1 × 1013, 1 × 1014 ions/cm2 to observe the effect of irradiation on structural properties and cationic distribution. XRD confirms the formation of single phase nanocrystalline cubic spinel ferrites with Scherrer's particle diameter (D) ranging between 15.7 - 17.4 nm. Results very distinctly show the electronic energy loss induced changes in: - experimental and theoretical lattice parameter (aexp., ath.), tetrahedral and octahedral bond length (RA, RB), and shared tetrahedral and octahedral edge (dAE, dBE). The paper reports the generation of magnetic moment of Zn ferrite by swift heavy ion irradiation induced distortion at tetrahedral site.

Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity.

PubMed

Faraji, Masoud; Mohaghegh, Neda; Abedini, Amir

2018-01-01

A series of g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plates were fabricated via simple dipping of TiO 2 nanotubes/Ti in a solution containing SnCl 2 and g-C 3 N 4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C 3 N 4 -SnO 2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO 2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis illuminations. Detailed characterization and results of photocatalytic and antibacterial activity tests revealed that semiconductor coupling significantly affected the photocatalyst properties synthesized and hence their photocatalytic and antibacterial activities. Modification of TiO 2 nanotubes/Ti plates with g-C 3 N 4 -SnO 2 deposits resulted in enhanced photocatalytic activities in both chemical and microbial systems. The g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate exhibited the highest photocatalytic and antibacterial activity, probably due to the heterojunction between g-C 3 N 4 -SnO 2 and TiO 2 nanotubes/Ti in the ternary composite plate and thus lower electron/hole recombination rate. Based on the obtained results, a photocatalytic and an antibacterial mechanism for the degradation of E. coli bacteria and chemical pollutants over g-C 3 N 4 -SnO 2 /TiO 2 nanotubes/Ti plate were proposed and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of substrates on structural and optical properties of tin oxide (SnO2) nanostructures.

PubMed

Johari, Anima; Bhatnagar, M C; Rana, Vikas

2012-10-01

We report on controlling the morphology of tin oxide (SnO2) nanostructures and the study of the effect of surface morphology on structural and optical properties of SnO2 nanostuctures. In present work, Tin oxide (SnO2) nanostructures such as nanowires and nanorods have been grown by thermal evaporation of SnO2 powder. To demonstrate the effect of different substrates on the morphology of grown SnO2 nanostructures, the thermal evaporation of SnO2 powder was carried out on Si and gold catalyzed Si (Au/Si) substrates. The scanning-electron-microscopic analysis shows the growth of SnO2 nanowires on Au/Si substrate and growth of SnO2 nanorods on Si substrate. The scanning-and transmission-electron-microscopic analysis shows that the diameter of SnO2 nanowires and nanorods are about 70 nm and 95 nm respectively and their length is about 80 microm and 30 microm respectively. The vapor-liquid-solid (VLS) growth of SnO2 nanowires and vapor-solid (VS) growth of SnO2 nanorods is also confirmed with the help of TEM and EDX spectra. The synthesized SnO2 nanowires show tetragonal rutile structure of SnO2, whereas SnO2 nanorods show tetragonal rutile as well as cassiterite structure of SnO2. UV-Vis absorption spectra showed the optical band gaps of 4.1 eV and 3.8 eV for the SnO2 nanowires and the nanorods, respectively. The SnO2 nanowires and nanorods show photoluminescence with broad emission peaks centred at around 600 nm and 580 nm respectively. Raman spectra of SnO2 nanowires shows three Raman shifts (478, 632, 773 cm(-1)) corresponding to Eg, A1g and B2g vibration modes, whereas in Raman spectra of SnO2 nanorods, A1g peak is dramatically reduced and the B2g mode is totally quenched.

2D SnO2 Nanosheets: Synthesis, Characterization, Structures, and Excellent Sensing Performance to Ethylene Glycol

PubMed Central

Wan, Wenjin; Li, Yuehua; Ren, Xingping; Zhao, Yinping; Gao, Fan; Zhao, Heyun

2018-01-01

Two dimensional (2D)SnO2 nanosheets were synthesized by a substrate-free hydrothermal route using sodium stannate and sodium hydroxide in a mixed solvent of absolute ethanol and deionized water at a lower temperature of 130 °C. The characterization results of the morphology, microstructure, and surface properties of the as-prepared products demonstrated that SnO2 nanosheets with a tetragonal rutile structure, were composed of oriented SnO2 nanoparticles with a diameter of 6–12 nm. The X-ray diffraction (XRD) and high-resolution transmission electron microscope (FETEM) results demonstrated that the dominant exposed surface of the SnO2 nanoparticles was (101), but not (110). The growth and formation was supposed to follow the oriented attachment mechanism. The SnO2 nanosheets exhibited an excellent sensing response toward ethylene glycol at a lower optimal operating voltage of 3.4 V. The response to 400 ppm ethylene glycol reaches 395 at 3.4 V. Even under the low concentration of 5, 10, and 20 ppm, the sensor exhibited a high response of 6.9, 7.8, and 12.0 to ethylene glycol, respectively. The response of the SnO2 nanosheets exhibited a linear dependence on the ethylene glycol concentration from 5 to 1000 ppm. The excellent sensing performance was attributed to the present SnO2 nanoparticles with small size close to the Debye length, the larger specific surface, the high-energy exposed facets of the (101) surface, and the synergistic effects of the SnO2 nanoparticles of the nanosheets. PMID:29462938

Iron doped SnO2/Co3O4 nanocomposites synthesized by sol-gel and precipitation method for metronidazole antibiotic degradation.

PubMed

Agarwal, Shilpi; Tyagi, Inderjeet; Gupta, Vinod Kumar; Sohrabi, Maryam; Mohammadi, Sanaz; Golikand, Ahmad Nozad; Fakhri, Ali

2017-01-01

Sol-gel and precipitation reaction methods were used to synthesize Un-doped and Fe-doped SnO 2 /Co 3 O 4 nanocomposites under UV light; the synthesized nanocomposites were applied for the photocatalytic degradation of metronidazole antibiotic. The developed photo catalyst was well characterized using energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM), UV-Visible and photoluminescence (PL) spectroscopy. Effective parameters such as pH, photocatalyst dose and contact time was optimized and well investigated. From the obtained facts it is clear that the 98.3% of MTZ was degraded with in 15min, pH6 and 0.1g catalyst when the Fe molar ratio was 1:1 at %. As compared to results obtained from un-doped SnO 2 /Co 3 O 4 nanocomposites Fe doped SnO 2 /Co 3 O 4 nanocomposites possess greater photocatalytic efficiency. Copyright © 2016 Elsevier B.V. All rights reserved.

Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

NASA Astrophysics Data System (ADS)

Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

2015-06-01

Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.

Self-catalytic branch growth of SnO 2 nanowire junctions

NASA Astrophysics Data System (ADS)

Chen, Y. X.; Campbell, L. J.; Zhou, W. L.

2004-10-01

Multiple branched SnO2 nanowire junctions have been synthesized by thermal evaporation of SnO powder. Their nanostructures were studied by transmission electron microscopy and field emission scanning electron microcopy. It was observed that Sn nanoparticles generated from decomposition of the SnO powder acted as self-catalysts to control the SnO2 nanojunction growth. Orthorhombic SnO2 was found as a dominate phase in nanojunction growth instead of rutile structure. The branches and stems of nanojunctions were found to be an epitaxial growth by electron diffraction analysis and high-resolution electron microscopy observation. The growth directions of the branched SnO2 nanojunctions were along the orthorhombic [1 1 0] and [ 1 1 bar 0 ] . A self-catalytic vapor-liquid-solid growth mechanism is proposed to describe the growth process of the branched SnO2 nanowire junctions.

Facile synthesis of SnO2/α-Fe2O3 nanocomposite for supercapacitor capacitor applications

NASA Astrophysics Data System (ADS)

Rani, B. Jansi; Saravanakumar, B.; Ravi, G.; Yuvakkumar, R.

2018-05-01

Facile and economically viable one step hydrothermal route was adapted to synthesis SnO2/α-Fe2O3 nanocomposite with and without hexamine (HMT) as surfactant successfully. The formation of SnO2/α-Fe2O3 nanocomposite was confirmed through XRD, Raman, PL and FTIR studies. The presence of well defined XRD diffraction peaks of both SnO2 and α-Fe2O3 revealed the formation SnO2/α-Fe2O3 nanocomposite. The obtained characteristic Raman active (Eg+Eg+Eu+A2u) mode of vibrations confirmed the formation of SnO2/α-Fe2O3 nanocomposite. Photoluminescence study revealed the emission behavior of the product. Metal oxygen vibrations of Fe-O in both octahedral, tetrahedral sites and Sn-O were confirmed by the bands located at 466, 580 and 673 cm-1 respectively through FTIR. The spherical morphology of the product synthesized with and without the surfactant HMT has been revealed by SEM images. The electrochemical behavior of the product was investigated through CV and EIS studies in 1M Na2SO4 electrolyte solution and obtained the highest specific capacitance of 211.25 F/g at 5 mV for the surfactant assisted product.

Effect of pulsed and continuous ultrasound on structural and magnetic properties of nano-sized Ni0.4Cu0.2Zn0.4Fe2O4 ferrite

NASA Astrophysics Data System (ADS)

Hassen, Harzali; Adel, Megriche; Arbi, Mgaidi

2018-03-01

Ultrasound-assisted co-precipitation has been used to prepare nano-sized Ni0.4Cu0.2Zn0.4Fe2O4 ferrite. Continuous (C-US) and pulsed (P-US) ultrasound modes are used at constant frequency = 20 kHz, reaction time = 2 h and pulse durations of 10 s on and 10 s off. All experiments were conducted at two temperatures 90 and 100°C. Samples were characterized by X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), N2 adsorption isotherms at 77 k analysis (BET), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM) techniques. A nanocrystalline single-phase with particle size in the range 12-18 nm is obtained in both modes: continuous and pulsed ultrasound mode. FT-IR measurements show two absorption bands assigned to the tetrahedral and octahedral vibrations (ν1 and ν2) characteristics of cubic spinel ferrite. The specific surface area (S BET) is in the range of 110-140 m2 g-1 and an average pore size between 5.5 and 6.5 nm. The lowest values are obtained in pulsed mode. Finally, this work shows that the magnetic properties are affected by the ultrasound conditions, without affecting the particle shape. The saturation magnetization (Ms) values obtained for all samples are comparable. In P-US mode, the saturation magnetization (Ms) increases as temperature increases. Moreover, P-US mode opens a new avenue for synthesis of NiCuZn ferrites.

In-situ deposition of hematite (α-Fe2O3) microcubes on cotton cellulose via hydrothermal method

NASA Astrophysics Data System (ADS)

Gili, M.; Latag, G.; Balela, M.

2018-03-01

Hematite microcubes with truncated edges have been successfully deposited on cotton cellulose via one-step hydrothermal process using anhydrous FeCl3 and glycine as Fe(III) precursor and chelating agent, respectively. The amount of glycine significantly affects the morphology and yield of hematite. The addition of 0.495 g of glycine to 50 ml of 0.1 M FeCl3 solution with 0.400 g of cotton resulted to hematite-deposited cellulose having ∼15% hematite content. The reduction of glycine to 0.247 g increased the amount of hematite on the surface of the cotton cellulose to ∼20% by weight. However, the hematite microcubes have a wide size distribution, with particle size in the range of 0.684 μm to 1.520 μm. Without glycine, hematite cannot be formed in the solution.

Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

PubMed

Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

2010-06-15

In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

FIB-tomographic studies on chemical vapor deposition grown SnO2 nanowire arrays on TiO2 (001)

NASA Astrophysics Data System (ADS)

Chen, Haoyun; Liu, Yi; Wu, Hong; Xiong, Xiang; Pan, Jun

2016-12-01

Tin oxide nanowire arrays on titania (001) have been successfully fabricated by chemical vapor deposition of Sn(O t Bu)4 precursor. The morphologies and structures of ordered SnO2 nanowires (NWs) were analyzed by cross-sectional SEM, HR-TEM and AFM. An FIB-tomography technique was applied in order to reconstruct a 3D presentation of ordered SnO2 nanowires. The achieved 3D analysis showed the spatial orientation and angles of ordered SnO2 NWs can be obtained in a one-shot experiment, and the distribution of Au catalysts showed the competition between 1D and 2D growth. The SnO2 nanowire arrays can be potentially used as a diameter- and surface-dependent sensing unit for the detection of gas- and bio-molecules.

Hydrothermally grown α-MnO2 interlocked mesoporous micro-cubes of several nanocrystals as selective and sensitive nitrogen dioxide chemoresistive gas sensors

NASA Astrophysics Data System (ADS)

Shinde, Pritamkumar V.; Xia, Qi Xun; Ghule, Balaji G.; Shinde, Nanasaheb M.; Seonghee, Jeong; Kim, Kwang Ho; Mane, Rajaram S.

2018-06-01

The interesting and multifunctional properties of alpha-manganese dioxide (α-MnO2) are considered to be highly sensitive and selective to nitrogen dioxide (NO2) chemresistive gas sensors. The α-MnO2 mesoporous interlocked micro-cubes composed of several interconnected nanocrystals synthesized by a facile and low-cost hydrothermal method on soda-lime glass substrate are envisaged as selective and sensitive NO2 gas sensors. Phase-purity and surface area with pore-size distribution are initially screened. The three-dimensional α-MnO2 mesoporous-cube-based gas sensors tested for NO2 gas from room-temperature (27 °C) to 250 °C have demonstrated 33% response for 100 ppm NO2 levels at 150 °C. The response and recovery time values of the α-MnO2 sensor are found to be 26 s and recovery 91 s, respectively, with high selectivity, good sensitivity, and considerable chemical and environmental stabilities, confirming the gas sensor applications potentiality of α-MnO2 morphology which is a combination of interlocked mesoporous micro-cubes and well-connected nanocrystals.

Highly sensitive SnO2 sensor via reactive laser-induced transfer

PubMed Central

Palla Papavlu, Alexandra; Mattle, Thomas; Temmel, Sandra; Lehmann, Ulrike; Hintennach, Andreas; Grisel, Alain; Wokaun, Alexander; Lippert, Thomas

2016-01-01

Gas sensors based on tin oxide (SnO2) and palladium doped SnO2 (Pd:SnO2) active materials are fabricated by a laser printing method, i.e. reactive laser-induced forward transfer (rLIFT). Thin films from tin based metal-complex precursors are prepared by spin coating and then laser transferred with high resolution onto sensor structures. The devices fabricated by rLIFT exhibit low ppm sensitivity towards ethanol and methane as well as good stability with respect to air, moisture, and time. Promising results are obtained by applying rLIFT to transfer metal-complex precursors onto uncoated commercial gas sensors. We could show that rLIFT onto commercial sensors is possible if the sensor structures are reinforced prior to printing. The rLIFT fabricated sensors show up to 4 times higher sensitivities then the commercial sensors (with inkjet printed SnO2). In addition, the selectivity towards CH4 of the Pd:SnO2 sensors is significantly enhanced compared to the pure SnO2 sensors. Our results indicate that the reactive laser transfer technique applied here represents an important technical step for the realization of improved gas detection systems with wide-ranging applications in environmental and health monitoring control. PMID:27118531

A comparative study of the magnetization in transition metal ion doped CeO2, TiO2 and SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

2018-05-01

Using the microscopic s-d model taking into account anharmonic spin-phonon interactions we have studied the magnetic properties of Co and Cu ion doped CeO2 and TiO2 nanoparticles and compared them with those of SnO2. By Co-doping there is a maximum in the magnetization M(x) curve for all nanoparticles observed in the most transition metal doped ones. The s-d interaction plays an important role by the decrease of M at higher dopant concentration. We have discussed the magnetization in dependence of different model parameters. By small Cu-ion doping there are some differences. In CeO2M decreases with the Cu-concentration, whereas in TiO2 and SnO2M increases. For higher Cu dopant concentrations M(X) decreases in TiO2 nanoparticles. We obtain room temperature ferromagnetism also in Zn doped CeO2, TiO2 and SnO2 nanoparticles, i.e. in non-transition metal ion doped ones. The different behavior of M in Co and Cu doped nanoparticles is due to a combination effect of multivalent metal ions, oxygen vacancies, different radius of cation dopants, connection between lattice and magnetism, as well as competition between the s-d and d-d ferromagnetic or antiferromagnetic interactions.

Effect of aging heat time and annealing temperature on the properties of nanocrystalline tin dioxide thin films

NASA Astrophysics Data System (ADS)

Kadhim, Imad H.; Abu Hassan, H.

2017-04-01

Nanocrystalline tin dioxide (SnO2) thin films have been successfully prepared by sol-gel spin-coating technique on p-type Si (100) substrates. A stable solution was prepared by mixing tin(II) chloride dihydrate, pure ethanol, and glycerin. Temperature affects the properties of SnO2 thin films, particularly the crystallite size where the crystallization of SnO2 with tetragonal rutile structure is achieved when thin films that prepared under different aging heat times are annealed at 400∘C. By increasing aging heat time in the presence of annealing temperatures the FESEM images indicated that the thickness of the fabricated film was directly proportional to solution viscosity, increasing from approximately 380 nm to 744 nm, as well as the crystallization of the thin films improved and reduced defects.

SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

NASA Astrophysics Data System (ADS)

Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

2017-05-01

Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

Atomic Layer Deposition of Electron Selective SnOx and ZnO Films on Mixed Halide Perovskite: Compatibility and Performance.

PubMed

Hultqvist, Adam; Aitola, Kerttu; Sveinbjörnsson, Kári; Saki, Zahra; Larsson, Fredrik; Törndahl, Tobias; Johansson, Erik; Boschloo, Gerrit; Edoff, Marika

2017-09-06

The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH 2 ) 2 , CH 3 NH 3 )Pb(I,Br) 3 (FAPbI 3 :MAPbBr 3 ) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnO x . Exposing the samples to the heat, the vacuum, and even the counter reactant of H 2 O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C 2 H 5 ) 2 either by itself or in combination with H 2 O during the ZnO atomic layer deposition (ALD) process is found to enhance the decomposition of the bulk of the perovskite film into PbI 2 without even forming ZnO. In contrast, the Sn precursor Sn(N(CH 3 ) 2 ) 4 does not seem to degrade the bulk of the perovskite film, and conformal SnO x films can successfully be grown on top of it using atomic layer deposition. Using this SnO x film as the electron selective layer in inverted perovskite solar cells results in a lower power conversion efficiency of 3.4% than the 8.4% for the reference devices using phenyl-C 70 -butyric acid methyl ester. However, the devices with SnO x show strong hysteresis and can be pushed to an efficiency of 7.8% after biasing treatments. Still, these cells lacks both open circuit voltage and fill factor compared to the references, especially when thicker SnO x films are used. Upon further investigation, a possible cause of these losses could be that the perovskite/SnO x interface is not ideal and more specifically found to be rich in Sn, O, and halides, which is probably a result of the nucleation during the SnO x growth and which might introduce barriers or alter the band alignment for the transport of charge carriers.

Spin canting and magnetic transition in NixZn1-xFe2O4 (x=0.0, 0.5 and 1.0) nanoparticles

NASA Astrophysics Data System (ADS)

Rani, Stuti; Raghav, Dharmendra Singh; Yadav, Prashant; Varma, G. D.

2018-04-01

Nanoparticles of NixZn1-xFe2O4(x=0.0, 0.5 and 1.0) have been synthesized via co-precipitation method and studied thestructural and magnetic properties. Rietveld refinement of X ray diffraction data of as synthesized samples revealthat the samples have mixed spinel structure with space group Fd-3m. The lattice parameter of the samples decreases as doping concentration of Ni ions increases. Magnetic measurements show paramagnetic to ferrimagnetic transition at room temperature on Ni doping in ZnFe2O4 nanoparticles. The magnetic measurements also show spin canting in samples possibly due to their nanocrystalline nature. The spin canting angles have been calculated with the help of Yafet-Kittel (Y-K) model. Furthermore, the Law of approach (LA) fitting of M-H curves indicates that the samples are highly anisotropicin nature. The Arrot plots of as synthesized samples also indicate the paramagnetic to ferrimagnetic transition. The correlation between the structural and observed magnetic properties of NixZn1-xFe2O4(x=0.0, 0.5 and 1.0) nanocrystals will be described and discussed in this paper.

Multi-applicative tetragonal TiO2/SnO2 nanocomposites for photocatalysis and gas sensing

NASA Astrophysics Data System (ADS)

Patil, S. M.; Dhodamani, A. G.; Vanalakar, S. A.; Deshmukh, S. P.; Delekar, S. D.

2018-04-01

TiO2-based mixed metal oxide heteronanostructures have multiple applications in photocatalysis and gas sensing because of their charge transport properties. In this study, we prepared tetragonal TiO2/SnO2 nanocomposites (NCs) with different weight percentages using a simple wet impregnation method. The physicochemical properties of the NCs were investigated using X-ray diffraction, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analysis. The results showed that the surface area of the NCs increased significantly and the anatase TiO2 was sensitized after the addition of a small amount of cassiterite SnO2 NPs. We systematically studied the as-prepared NCs during the photocatalytic degradation of Congo Red dye under visible light irradiation (λ > 420 nm) and NH3 gas sensing, which demonstrated the efficient photocatalytic performance and the superior sensing response of the catalyst with a weight composition of 25% SnO2 in TiO2 (4:1) compared with the other NCs or the bare individual nanoparticles. The improved photocatalytic and gas sensing performance of the TiO2/SnO2 (4:1) NCs may be attributed to the increased active surface area, the increased adsorption of the dye and target gas molecules, as well as efficient electron-hole charge separation and transfer.

Heterogeneous nanocrystals assembled TiO2/SnO2/C composite for improved lithium storage

NASA Astrophysics Data System (ADS)

Tian, Qinghua; Mao, Yuning; Zhang, Xuzhen; Yang, Li

2018-07-01

Using stable TiO2 and flexible carbon as double-functional structure protector of nanostructural SnO2 to fabricate TiO2/SnO2/C composites is widely considered as a favorable strategy for improving the lithium storage performance of SnO2 anodes. But, it is still a challenge to obtain a satisfying TiO2/SnO2/C composite. Herein, an interesting porous nanostructure of TiO2/SnO2/C nanosphere composite assembled by TiO2 and SnO2 nanocrystals with an outer carbon coating has been fabricated by a well-designed approach. Thanks to the perfectly combined action of porous spherical nanostructure, TiO2 and SnO2 nanocrystals and carbon coating, the as-prepared composite obtains excellent structure stability and improved electrochemcial properties. When used as a promising anode for lithium-ion batteres, it exhibits outstanding lithium storage performance, delivering a high capacity of 687.2 mAh g-1 after even 400 cycles.

Enhancement of visible light photocatalytic activity over bistructural SnO2 nanobelts

NASA Astrophysics Data System (ADS)

Wang, Lihua; Wang, Yongli; Su, Dezhi; Zhao, Yongjie

2018-02-01

SnO2 nanobelts were synthesized by hydrothermal method. The structure and morphology were investigated by XRD, Raman spectra, SEM and TEM. The results revealed that the synthesized SnO2 nanobelts were covered with amorphous surface. For the photocatalytic efficiency of methylene blue, the none-fully crystallized SnO2 nanobelts were over four times higher than bulk SnO2. Moreover, the photo-degradation rate constant with SnO2 nanobelts as photocatalysts was over six times higher than bulk SnO2. It was considered that the subtle structure of SnO2 nanobelts not only lowered the band gap but also improved the transfer of charge carriers and trapping effect of solar light. Furthermore, this strategy of enhancing photocatalytic performance could be extended to the other kinds of metal oxide photocatalyst.

Structural and magnetic properties of sol-gel Co2xNi0.5-x Zn0.5-xFe2O4 thin films

NASA Astrophysics Data System (ADS)

Rebrov, Evgeny V.; Gao, Pengzhao; Verhoeven, Tiny M. W. G. M.; Schouten, Jaap C.; Kleismit, Richard; Turgut, Zafer; Kozlowski, Gregory

2011-03-01

Nanocrystalline Co2xNi0.5-xZn0.5-xFe2O4 (x=0-0.5) thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology as well as magnetic and microwave absorption properties of the films calcined at 1073 K were studied using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. All films were uniform without microcracks. The Co content in the Co-Ni-Zn films resulted in a grain size ranging from 15 to 32 nm while it ranged from 33 to 49 nm in the corresponding powders. Saturation and remnant magnetization increased with increase in grain size, while coercivity demonstrated a drop due to multidomain behavior of crystallites for a given value of x. Saturation magnetization increased and remnant magnetization had a maximum as a function of grain size independent of x. In turn, coercivity increased with x independent of grain size. Complex permittivity of the Co-Ni-Zn ferrite films was measured in the frequency range 2-15 GHz. The highest hysteretic heating rate in the temperature range 315-355 K was observed in CoFe2O4. The maximum absorption band shifted from 13 to 11 GHz as cobalt content increased from x=0.1 to 0.2.

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

NASA Astrophysics Data System (ADS)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

Tuning the optical bandgap in multi-cation compound transparent conducting-oxides: The examples of In2ZnO4 and In4Sn3O12

NASA Astrophysics Data System (ADS)

Sabino, Fernando P.; Oliveira, Luiz N.; Wei, Su-Huai; Da Silva, Juarez L. F.

2018-02-01

Transparent conducting oxides such as the bixbyite In2O3 and rutile SnO2 systems have large disparities between the optical and fundamental bandgaps, ΔEgO F , because selection rules forbid dipolar transitions from the top of the valence band to the conduction-band minimum; however, the optical gaps of multi-cation compounds with the same chemical species often coincide with their fundamental gaps. To explain this conundrum, we have employed density-functional theory to compute the optical properties of multi-cation compounds, In2ZnO4 and In4Sn3O12, in several crystal structures. We show that a recently proposed mechanism to explain the disparity between the optical and fundamental gaps of M2O3 (M = Al, Ga, and In) applies also to other binary systems and to multi-compounds. Namely, a gap disparity will arise if the following three conditions are satisfied: (i) the crystal structure has inversion symmetry; (ii) the conduction-band minimum is formed by the cation and O s-orbitals; and (iii) there is strong p-d coupling and weak p-p in the vicinity of the valence-band maximum. The third property depends critically on the cationic chemical species. In the structures with inversion symmetry, Zn (Sn) strengthens (weakens) the p-d coupling in In2ZnO4 (In4Sn3O12), enhancing (reducing) the gap disparity. Furthermore, we have also identified a In4Sn3O12 structure that is 31.80 meV per formula unit more stable than a recently proposed alternative model.

Inelastic neutron scattering investigation of low temperature phase transition in Rb2ZnCl4 and K2ZnCl4

NASA Astrophysics Data System (ADS)

Quilichini, M.; Dvořák, V.; Boutrouille, P.

1991-09-01

Inelastic scattering of neutrons has revealed soft optic modes at the T point frac{1}{2}({b}^*+{c}^*) of the Brillouin zone both in Rb2ZnCl4 and K2ZnCl4 which are responsible for the phase transition from the ferroelectric to the lowest temperature phase of these materials. Moreover, in K2ZnCl4 near the T point a minimum on the soft optic branch in the direction (μ{b}^*+frac{1}{2}{c}^*) has been found which confirms the existence of a new incommensurate phase recently discovered by Gesi. The origin of this incommensurate phase is discussed from a phenomenological point of view and formulae for elastic constants are derived describing their behaviour near transition into incommensurate phase. Des mesures de diffusion inélastique des neutrons ont mis en évidence l'existence d'un mode optique mou au point T(frac{1}{2}({b}^*+{c}^*)) de la zone de Brillouin responsable de la transition de la phase ferroélectrique vers la phase basse température dans les deux composés Rb2ZnCl4 and K2ZnCl4. Pour K2ZnCl4 on montre que la branche optique molle présente un minimum au voisinage de T dans la direction (μ{b}^*+frac{1}{2}{c}^*), ce qui confirme l'existence de la nouvelle phase incommensurable récemment trouvée par Gesi. L'origine de cette phase est discutée sur la base d'un modèle phénoménologique dont on dérive aussi les formules des constantes élastiques et leur comportement au voisinage de la transition vers la phase incommensurable.

Metallic Sn spheres and SnO2@C core-shells by anaerobic and aerobic catalytic ethanol and CO oxidation reactions over SnO2 nanoparticles

PubMed Central

Kim, Won Joo; Lee, Sung Woo; Sohn, Youngku

2015-01-01

SnO2 has been studied intensely for applications to sensors, Li-ion batteries and solar cells. Despite this, comparatively little attention has been paid to the changes in morphology and crystal phase that occur on the metal oxide surface during chemical reactions. This paper reports anaerobic and aerobic ethanol and CO oxidation reactions over SnO2 nanoparticles (NPs), as well as the subsequent changes in the nature of the NPs. Uniform SnO2@C core-shells (10 nm) were formed by an aerobic ethanol oxidation reaction over SnO2 NPs. On the other hand, metallic Sn spheres were produced by an anaerobic ethanol oxidation reaction at 450 °C, which is significantly lower than that (1200 °C) used in industrial Sn production. Anaerobic and aerobic CO oxidation reactions were also examined. The novelty of the methods for the production of metallic Sn and SnO2@C core-shells including other anaerobic and aerobic reactions will contribute significantly to Sn and SnO2-based applications. PMID:26300041

Sonochemical synthesis of 1,2,4,5-tetrasubstituted imidazoles using nanocrystalline MgAl2O4 as an effective catalyst☆

PubMed Central

Safari, Javad; Gandomi-Ravandi, Soheila; Akbari, Zahra

2012-01-01

An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate and primary aromatic amine with nanocrystalline magnesium aluminate in ethanol under ultrasonic irradiation. High yields, short reaction times, mild conditions, simplicity of operation and easy work-up are some advantages of this protocol. PMID:25685459

Ordered mesoporous MFe(2)O(4) (M = Co, Cu, Mg, Ni, Zn) thin films with nanocrystalline walls, uniform 16 nm diameter pores and high thermal stability: template-directed synthesis and characterization of redox active trevorite.

PubMed

Haetge, Jan; Suchomski, Christian; Brezesinski, Torsten

2010-12-20

In this paper, we report on ordered mesoporous NiFe(2)O(4) thin films synthesized via co-assembly of hydrated ferric nitrate and nickel chloride with an amphiphilic diblock copolymer, referred to as KLE. We establish that the NiFe(2)O(4) samples are highly crystalline after calcination at 600 °C, and that the conversion of the amorphous inorganic framework comes at little cost to the ordering of the high quality cubic network of pores averaging 16 nm in diameter. We further show that the synthesis method employed in this work can be readily extended to other ferrites, such as CoFe(2)O(4), CuFe(2)O(4), MgFe(2)O(4), and ZnFe(2)O(4), which could pave the way for innovative device design. While this article focuses on the self-assembly and characterization of these materials using various state-of-the-art techniques, including electron microscopy, grazing incidence small-angle X-ray scattering (GISAXS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), as well as UV-vis and Raman spectroscopy, we also examine the electrochemical properties and show the benefits of combining a continuous mesoporosity with nanocrystalline films. KLE-templated NiFe(2)O(4) electrodes exhibit reasonable levels of lithium ion storage at short charging times which stem from facile pseudocapacitance.

Impact of Substrate Types on Structure and Emission of ZnO Nanocrystalline Films

NASA Astrophysics Data System (ADS)

Ballardo Rodriguez, I. Ch.; El Filali, B.; Díaz Cano, A. I.; Torchynska, T. V.

2018-02-01

Zinc oxide (ZnO) films were simultaneously synthesized by an ultrasonic spray pyrolysis (USP) method on p-type Si (100), silicon carbide polytype [6H-SiC (0001)], porous 6H-SiC and amorphous glass substrates with the aim of studying the impact of substrate types on the structure and emission of ZnO nanocrystalline films. Porous silicon carbide (P-SiC) was prepared by the electrochemical anodization method at a constant potential of 20 V and etching time of 12 min. ZnO films grown on the SiC and P-SiC substrates are characterized by a wurtzite crystal structure with preferential growth along the (002) direction and with grain sizes of 90-180 and 70-160 nm, respectively. ZnO films grown on the Si substrate have just some small irregular hexagonal islands. The amorphous glass substrate did not promote the formation of any regular crystal forms. The obtained x-ray diffraction and photoluminescence (PL) results have shown that the better ZnO film crystallinity and high PL intensity of near-band edge emissions were achieved in the films grown on the porous SiC and SiC substrates. The preferential growth and crystalline nature of ZnO films on the SiC substrate have been discussed from the point of view of the lattice parameter compatibility between ZnO and SiC crystals.

Preparation and characterization of ZnS thin films by the chemical bath deposition method (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ando, Shizutoshi; Iwashita, Taisuke

2017-06-01

Nowadays, the conversion efficiency of Cu(In･Ga)Se2 (CIGS)-based solar cell already reached over 20%. CdS thin films prepared by chemical bath deposition (CBD) method are used for CIGS-based thin film solar cells as the buffer layer. Over the past several years, a considerable number of studies have been conducted on ZnS buffer layer prepared by CBD in order to improve in conversion efficiency of CIGS-based solar cells. In addition, application to CIGS-based solar cell of ZnS buffer layer is expected as an eco-friendly solar cell by cadmium-free. However, it was found that ZnS thin films prepared by CBD included ZnO or Zn(OH)2 as different phase [1]. Nakata et. al reported that the conversion efficiency of CIGS-based solar cell using ZnS buffer layer (CBD-ZnS/CIGS) reached over 18% [2]. The problem which we have to consider next is improvement in crystallinity of ZnS thin films prepared by CBD. In this work, we prepared ZnS thin films on quarts (Si02) and SnO2/glass substrates by CBD with the self-catalysis growth process in order to improve crystallinity and quality of CBD-ZnS thin films. The solution to use for CBD were prepared by mixture of 0.2M ZnI2 or ZnSO4, 0.6M (NH2)2CS and 8.0M NH3 aq. In the first, we prepared the particles of ZnS on Si02 or SnO2/glass substrates by CBD at 80° for 20 min as initial nucleus (1st step ). After that, the particles of ZnS on Si02 or SnO2/glass substrates grew up to be ZnS thin films by CBD method at 80° for 40 min again (2nd step). We found that the surface of ZnS thin films by CBD with the self-catalyst growth process was flat and smooth. Consequently, we concluded that the CBD technique with self-catalyst growth process in order to prepare the particles of ZnS as initial nucleus layer was useful for improvement of crystallinity of ZnS thin films on SnO2/glass. [1] J.Vidal et,al., Thin Solid Films 419 (2002) 118. [2] T.Nakata et.al., Jpn. J. Appl. Phys. 41(2B), L165-L167 (2002)

A detailed study on Sn4+ doped ZnO for enhanced photocatalytic degradation

NASA Astrophysics Data System (ADS)

Beura, Rosalin; Pachaiappan, R.; Thangadurai, P.

2018-03-01

The samples of Sn4+ doped (1, 5, 10, 15, 20 & 30%) ZnO nanostructures were synthesized by a low temperature hydrothermal method. Structural analysis by XRD and Raman spectroscopy showed the hexagonal wurtzite phase of ZnO and the formation of a secondary phase Zn2SnO4 beyond 10% doping of Sn4+. Microstructural analysis by TEM also confirmed the wurtzite ZnO with rod as well as particle like structure. Presence of various functional groups (sbnd OH, sbnd CH, Znsbnd O) were confirmed by FTIR. Optical properties were studied by UV-vis absorption, photoluminescence emission spectroscopies and lifetime measurement. Band gap of the undoped and Sn4+ doped ZnO were analyzed by Tauc plot and it was observed that the band gap of the materials had slightly decreased from 3.2 to 3.16 eV and again increased to 3.23 eV with respect to the increase in the doping concentration from 1 to 30%. A significant change was also noticed in the photoluminescence emission properties of ZnO i.e. increase in the intensity of NBE emission and decrease in DLE, on subject to Sn4+ doping. Average PL lifetime had increased from 29.45 ns for ZnO to 30.62 ns upon 1% Sn ion doping in ZnO. Electrical properties studied by solid state impedance spectroscopy showed that the conductivity had increased by one order of magnitude (from 7.48×10-8 to 2.21×10-7 S/cm) on Sn4+ doping. Photocatalytic experiments were performed on methyl orange (MO) as a model industrial dye under UV light irradiation for different irradiation times. The optimum Sn4+ content in order to achieve highest photocatalytic activity was found to be 1% Sn 4+ doping. The enhancement was achieved due to a decrease in the band gap favoring the generation of electron-hole pairs and the enhanced PL life time that delays the recombination of these charge carrier formation. The third reason was that the increased electrical conductivity that indicated the faster charge transfer in this material to enhance the photocatalytic activity. The Sn

Fuel additives and heat treatment effects on nanocrystalline zinc ferrite phase composition

NASA Astrophysics Data System (ADS)

Hu, Ping; Pan, De-an; Wang, Xin-feng; Tian, Jian-jun; Wang, Jian; Zhang, Shen-gen; Volinsky, Alex A.

2011-03-01

Nanocrystalline ZnFe 2O 4 powder was prepared by the auto-combustion method using citric acid, acetic acid, carbamide and acrylic acid as fuel additives. Pure spinel zinc ferrite with the crystallite size of about 15 nm can be obtained by using acrylic acid as fuel additive. Samples prepared using other fuel additives contain ZnO impurities. In order to eliminate ZnO impurities, the sample prepared with citric acid as fuel additive was annealed at different temperatures up to 1000 °C in air and in argon. Annealed powders have pure ZnFe 2O 4 phase when annealing temperature is higher than 650 °C in air. Sample annealed at 650 °C in air is paramagnetic. However, annealed powders become a mixture of Fe 3O 4 and FeO after annealing at 1000 °C in argon atmosphere due to Zn volatility and the reduction reaction.

Fabrication of Cu2ZnSn(S,Se)4 (CZTSSe) absorber films based on solid-phase synthesis and blade coating processes

NASA Astrophysics Data System (ADS)

Ma, Ruixin; Yang, Fan; Li, Shina; Zhang, Xiaoyong; Li, Xiang; Cheng, Shiyao; Liu, Zilin

2016-04-01

CZTSSe is an important earth abundant collection of materials for the development of low cost and high efficiency thin film solar cells. This work developed a simple non-vacuum-based route to fabricate CZTSSe absorber films. This was demonstrated by first synthesizing Cu2ZnSnS4 (CZTS) nano-crystalline based on solid-phase synthesis. Then a stable colloidal ink composed of CZTS nano-crystalline was blade coated on Mo-coated substrates followed by an annealing process under Ar atmosphere. After CZTS films formation, the films were sintered into CZTSSe absorber films by exposing them under Selenium vapor. The formation of a kesterite type CZTS was confirmed using X-ray diffraction and Raman scattering measurements. The band gap of CZTSSe absorber films was determined to be 1.26 eV, which was appropriate for use as an absorber layer in thin film solar cells. The CZTSSe absorber films showed a good photovoltatic performance, demonstrating this simple approach had great potential for CZTSSe solar cell production.

Remediation of arsenic and lead with nanocrystalline zinc sulfide.

PubMed

Piquette, Alan; Cannon, Cody; Apblett, Allen W

2012-07-27

Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

The Phase Relations in the In 2O 3-Al 2ZnO 4-ZnO System at 1350°C

NASA Astrophysics Data System (ADS)

Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko; Isobe, Mitsumasa

1993-08-01

Phase relations in the In 2O 3-Al 2ZnO 4-ZnO system at 1350°C are determined by a classical quenching method. This system consists of In 2O 3, Al 2ZnO 4, ZnO, and homologous phases InAlO 3(ZnO) m ( m = 2, 3, …) having solid solutions with LuFeO 3(ZnO) m-type crystal structures. These solid solution ranges are as follows: In 1+ x1Al 1- x1O 3(ZnO) 2 ( x1 = 0.70)-In 1+ x2Al 1- x2O 3(ZnO) 2 ( x2 = 0.316-0.320), In 2O 3(ZnO) 3-In 1+ xAl 1- xO 3(ZnO) 3 ( x = 0.230), In 2O 3(ZnO) 4-In 1+ xAl 1- xO 3(ZnO) 4 ( x = 0.15-0.16), In 2O 3(ZnO) 5-In 1+ xAl 1- xO 3(ZnO) 5 ( x = 0.116-0.130), In 2O 3(ZnO) 6-In 1+ xAl 1- xO 3(ZnO) 6 ( x = 0.000-0.111), In 2O 3(ZnO) 7-In 1+ xAl 1- xO 3(ZnO) 7 ( x = 0.08), In 2O 3(ZnO) 8-In 1+ xAl 1- xO 3(ZnO) 8 ( x: undetermined), and In 2O 3(ZnO) m-InAlO 3(ZnO) m ( m = 9, 10, 11, 13, 15, 17, and 19). The space groups of these homologous phases belong to R3¯ m for m = odd or P6 3/ mmc for m = even. Their crystal structures, In 1+ xAl 1- xO 3(ZnO) m (0 < x < 1), consist of three kinds of layers: an InO 1.5 layer, an (In xAl 1- xZn)O 2.5 layer, and ZnO layers. A comparison of the phase relations in the In 2O 3- M2ZnO 4-ZnO systems ( M = Fe, Ga, or Al) is made and their characteristic features are discussed in terms of the ionic radii and site preferences of the M cations.

Magnetic micro scavengers: highly porous Ni1-x Co x Fe2O4 microcubes for efficient disintegration of nitrophenol.

PubMed

Pervaiz, Erum; Virk, Muhammad Syam Azhar; Tareen, Ayesha Khan; Zhang, Bingxue; Zhao, Qiuyan; Wang, Zhenzhen; Yang, Minghui

2018-05-25

The fabrication of functional materials in patterned morphology is focused to obtain remarkable physiognomies of the materials for certain applications. Instead of randomly distributed agglomerated nanoparticles, it is highly desirable to arrange them in a motif, as this directed formation of nanomaterials can have a substantial influence on their performance and activity in various applications. With this perspective, MOF derived hollow cubes of nickel cobalt ferrites have been synthesized via a facile process using sacrificial templates at 600 °C. Microcubes, composed of tiny grains in a size range from 10 nm ± 2 nm were obtained in pure form as a polycrystalline material. The high specific surface area (1185 m 2 g -1 ) and mesoporous nature of hollow cubic ferrites were found to be excellent adsorbents for nitrophenol at room temperature. The equilibrium quantity of adsorbed nitrophenol was calculated as 47 mg g -1 ferrite, accomplished in 7 min. Their large surface area, mesopores and hollow nature, in combination with controlled size distribution of grains, have enabled this remarkable utilization of nanoferrites for removal of nitrophenol from water.

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

NASA Astrophysics Data System (ADS)

Drake, Christina Hartsell

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature

Enhanced room temperature ferromagnetism in Ni doped SnO2 nanoparticles: A comprehensive study

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Ali, T.; Naseem Siddique, M.; Ahmad, Abid; Tripathi, P.

2017-08-01

We emphasized on a detailed investigation of the structural, optical, and magnetic properties of pure and Ni-doped SnO2 nanoparticles (NPs) synthesized by a sol-gel process. An extensive structural study has been carried out using various characterization techniques. The X-ray Diffraction (XRD) spectra show the formation of the single phase tetragonal structure of pure and Ni-doped SnO2 NPs without any noticeable impurity phase such as NiO. XRD results indicate that the crystallite size of SnO2 is found to be decreased with Ni doping, which has also been confirmed by the Field Emission Scanning Electron Microscopy study. X-ray Photoelectron Spectroscopy (XPS) measurements displayed a clear sign for Ni2+ ions occupying the lattice sites of Sn4+ in the SnO2 host which also gives clear evidence for the formation of single phase Sn1-xNixO2 NPs. The optical analysis shows a significant decrease in the energy gap of SnO2, i.e., (from 3.71 eV to 3.28 eV) as Ni concentration increases which may be correlated with the core level valence band XPS analysis. Photoluminescence studies show that Ni doping creates oxygen vacancies due to dissimilar ionic radii of Ni2+ and Sn4+. Superconducting quantum interference device measurements revealed that the Ni doped SnO2 NPs exhibit strong ferromagnetic behavior at room temperature and this analysis has been well fitted with a simple relationship to find out magnetic parameters proposed by Stearns and Cheng et al. Hence, our results demonstrate that Ni-doping has strong impact on the structural, optical, and magnetic properties.

Porous SnO2-CuO nanotubes for highly reversible lithium storage

NASA Astrophysics Data System (ADS)

Cheong, Jun Young; Kim, Chanhoon; Jung, Ji-Won; Yoon, Ki Ro; Kim, Il-Doo

2018-01-01

Facile synthesis of rationally designed structures is critical to realize a high performance electrode for lithium-ion batteries (LIBs). Among different candidates, tin(IV) oxide (SnO2) is one of the most actively researched electrode materials due to its high theoretical capacity (1493 mAh g-1), abundance, inexpensive costs, and environmental friendliness. However, severe capacity decay from the volume expansion and low conductivity of SnO2 have hampered its use as a feasible electrode for LIBs. Rationally designed SnO2-based nanostructures with conductive materials can be an ideal solution to resolve such limitations. In this work, we have successfully fabricated porous SnO2-CuO composite nanotubes (SnO2-CuO p-NTs) by electrospinning and subsequent calcination step. The porous nanotubular structure is expected to mitigate the volume expansion of SnO2, while the as-formed Cu from CuO upon lithiation allows faster electron transport by improving the low conductivity of SnO2. With a synergistic effect of both Sn and Cu-based oxides, SnO2-CuO p-NTs deliver stable cycling performance (91.3% of capacity retention, ∼538 mAh g-1) even after 350 cycles at a current density of 500 mA g-1, along with enhanced rate capabilities compared with SnO2.

Flexible High-Performance Lead-Free Na0.47K0.47Li0.06NbO3 Microcube-Structure-Based Piezoelectric Energy Harvester.

PubMed

Gupta, Manoj Kumar; Kim, Sang-Woo; Kumar, Binay

2016-01-27

Lead-free piezoelectric nano- and microstructure-based generators have recently attracted much attention due to the continuous demand of self-powered body implantable devices. We report the fabrication of a high-performance flexible piezoelectric microgenerator based on lead-free inorganic piezoelectric Na0.47K0.47Li0.06NbO3 (NKLN) microcubes for the first time. The composite generator is fabricated using NKLN microcubes and polydimethylsiloxane (PDMS) polymer on a flexible substrate. The flexible device exhibits excellent performance with a large recordable piezoelectric output voltage of 48 V and output current density of 0.43 μA/cm(2) under vertical compressive force of 2 kgf, for which an energy conversion efficiency of about 11% has been achieved. Piezoresponse and ferroelectric studies reveal that NKLN microcubes exhibited high piezoelectric charge coefficient (d33) as high as 460 pC/N and a well-defined hysteresis loops with remnant polarization and coercive field of 13.66 μC/cm(2) and 19.45 kV/cm, respectively. The piezoelectric charge generation mechanism from NKLN microgenerator are discussed in the light of the high d33 and alignment of electric dipoles in polymer matrix and dielectric constant of NKLN microcubes. It has been demonstrated that the developed power generator has the potential to generate high electric output power under mechanical vibration for powering biomedical devices in the near future.

Thermoelectric Properties of Self Assembled TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 W/mK2 at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Soft exfoliation of 2D SnO with size-dependent optical properties

NASA Astrophysics Data System (ADS)

Singh, Mandeep; Della Gaspera, Enrico; Ahmed, Taimur; Walia, Sumeet; Ramanathan, Rajesh; van Embden, Joel; Mayes, Edwin; Bansal, Vipul

2017-06-01

Two-dimensional (2D) materials have recently gained unprecedented attention as potential candidates for next-generation (opto)electronic devices due to their fascinating optical and electrical properties. Tin monoxide, SnO, is an important p-type semiconductor with applications across photocatalysis (water splitting) and electronics (transistors). However, despite its potential in several important technological applications, SnO remains underexplored in its 2D form. Here we present a soft exfoliation strategy to produce 2D SnO nanosheets with tunable optical and electrical properties. Our approach involves the initial synthesis of layered SnO microspheres, which are readily exfoliated through a low-power sonication step to form high quality SnO nanosheets. We demonstrate that the properties of 2D SnO are strongly dependent on its dimensions. As verified through optical absorption and photoluminescence studies, a strong size-dependent quantum confinement effect in 2D SnO leads to substantial variation in its optical and electrical properties. This results in a remarkable (>1 eV) band gap widening in atomically thin SnO. Through photoconductivity measurements, we further validate a strong correlation between the quantum-confined properties of 2D SnO and the selective photoresponse of atomically thin sheets in the high energy UV light. Such tunable semiconducting properties of 2D SnO could be exploited for a variety of applications including photocatalysis, photovoltaics and optoelectronics in general.

Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO2 photoanodes

PubMed Central

Basu, Kaustubh; Benetti, Daniele; Zhao, Haiguang; Jin, Lei; Vetrone, Fiorenzo; Vomiero, Alberto; Rosei, Federico

2016-01-01

We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO2) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiOx or TiCl4 precursor solutions to create a blocking layer before tape casting the SnO2 mesoporous anode. In addition, SnO2 photoelectrodes were treated with the same precursor solutions to deposit a TiO2 passivating layer covering the SnO2 particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl4 treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO2 anode by titania can play a major role in maximizing the photo conversion efficiency. PMID:26988622

Thermoelectric Properties of Self Assemble TiO2/SnO2 Nanocomposites

NASA Technical Reports Server (NTRS)

Dynys, Fred; Sayir, Ali; Sehirlioglu, Alp

2008-01-01

Recent advances in improving efficiency of thermoelectric materials are linked to nanotechnology. Thermodynamically driven spinodal decomposition was utilized to synthesize bulk nanocomposites. TiO2/SnO2 system exhibits a large spinodal region, ranging from 15 to 85 mole % TiO2. The phase separated microstructures are stable up to 1400 C. Semiconducting TiO2/SnO2 powders were synthesized by solid state reaction between TiO2 and SnO2. High density samples were fabricated by pressureless sintering. Self assemble nanocomposites were achieved by annealing at 1000 to 1350 C. X-ray diffraction reveal phase separation of (Ti(x)Sn(1-x))O2 type phases. The TiO2/SnO2 nanocomposites exhibit n-type behavior; a power factor of 70 (mu)W/m sq K at 1000 C has been achieved with penta-valent doping. Seebeck, thermal conductivity, electrical resistivity and microstructure will be discussed in relation to composition and doping.

Nanocrystalline ZnON; High mobility and low band gap semiconductor material for high performance switch transistor and image sensor application

PubMed Central

Lee, Eunha; Benayad, Anass; Shin, Taeho; Lee, HyungIk; Ko, Dong-Su; Kim, Tae Sang; Son, Kyoung Seok; Ryu, Myungkwan; Jeon, Sanghun; Park, Gyeong-Su

2014-01-01

Interest in oxide semiconductors stems from benefits, primarily their ease of process, relatively high mobility (0.3–10 cm2/vs), and wide-bandgap. However, for practical future electronic devices, the channel mobility should be further increased over 50 cm2/vs and wide-bandgap is not suitable for photo/image sensor applications. The incorporation of nitrogen into ZnO semiconductor can be tailored to increase channel mobility, enhance the optical absorption for whole visible light and form uniform micro-structure, satisfying the desirable attributes essential for high performance transistor and visible light photo-sensors on large area platform. Here, we present electronic, optical and microstructural properties of ZnON, a composite of Zn3N2 and ZnO. Well-optimized ZnON material presents high mobility exceeding 100 cm2V−1s−1, the band-gap of 1.3 eV and nanocrystalline structure with multiphase. We found that mobility, microstructure, electronic structure, band-gap and trap properties of ZnON are varied with nitrogen concentration in ZnO. Accordingly, the performance of ZnON-based device can be adjustable to meet the requisite of both switch device and image-sensor potentials. These results demonstrate how device and material attributes of ZnON can be optimized for new device strategies in display technology and we expect the ZnON will be applicable to a wide range of imaging/display devices. PMID:24824778

Designed hybrid nanostructure with catalytic effect: beyond the theoretical capacity of SnO2 anode material for lithium ion batteries

PubMed Central

Wang, Ye; Huang, Zhi Xiang; Shi, Yumeng; Wong, Jen It; Ding, Meng; Yang, Hui Ying

2015-01-01

Transition metal cobalt (Co) nanoparticle was designed as catalyst to promote the conversion reaction of Sn to SnO2 during the delithiation process which is deemed as an irreversible reaction. The designed nanocomposite, named as SnO2/Co3O4/reduced-graphene-oxide (rGO), was synthesized by a simple two-step method composed of hydrothermal (1st step) and solvothermal (2nd step) synthesis processes. Compared to the pristine SnO2/rGO and SnO2/Co3O4 electrodes, SnO2/Co3O4/rGO nanocomposites exhibit significantly enhanced electrochemical performance as the anode material of lithium-ion batteries (LIBs). The SnO2/Co3O4/rGO nanocomposites can deliver high specific capacities of 1038 and 712 mAh g−1 at the current densities of 100 and 1000 mA g−1, respectively. In addition, the SnO2/Co3O4/rGO nanocomposites also exhibit 641 mAh g−1 at a high current density of 1000 mA g−1 after 900 cycles, indicating an ultra-long cycling stability under high current density. Through ex-situ TEM analysis, the excellent electrochemical performance was attributed to the catalytic effect of Co nanoparticles to promote the conversion of Sn to SnO2 and the decomposition of Li2O during the delithiation process. Based on the results, herein we propose a new method in employing the catalyst to increase the capacity of alloying-dealloying type anode material to beyond its theoretical value and enhance the electrochemical performance. PMID:25776280

Preparation of ZnO/SnO2 Composite Nanometer Photocatalyst and Photocatalytic Treatment of Marine Diesel Pollution

NASA Astrophysics Data System (ADS)

Zhang, J.; Yu, X. C.; Nie, Z. W.; Guo, M. C.; Liu, J. H.; Wang, L. P.

2017-12-01

The ZnO/SnO2 composite nanophotocatalyst studied in this paper was prepared by a chemical precipitation method, which were characterized by XRD and SEM. The results show that the prepared samples were rutile SnO2 particles and the average grain size is 8.41 nm. In this paper, the factors for the degradation efficiency of marine diesel oil degraded by ZnO/SnO2 composite nanophotocatalyst are the catalysts’ doping ratio, the initial concentration of oil, the pH value of seawater, the dosage of catalyst and the dosage of hydrogen peroxide. The results show that the ZnO/SnO2 composite nanophotocatalyst can effectively degrade seawater diesel oil under UV light. When the doping ratio of ZnO and SnO2 is 0.35, the reaction time is 2.5 hours, the pH value of seawater with oil is 7, The concentration of diesel oil is 0.1g/L, the dosage of catalyst is 0.3g/L and the dosage of hydrogen peroxide is 0.1 g/L, the highest degradation rate is 91.54%.

Synthesis and characterization of (Sn,Zn)O alloys

DOE PAGES

Bikowski, Andre; Holder, Aaron; Peng, Haowei; ...

2016-09-29

SnO exhibits electrical properties that render it promising for solar energy conversion applications, but it also has a strongly indirect band gap. Recent theoretical calculations predict that this disadvantage can be mitigated by isovalent alloying with other group-II oxides such as ZnO. Here, we synthesized new metastable isovalent (Sn,Zn)O alloy thin films by combinatorial reactive co-sputtering and characterized their structural, optical and electrical properties. The alloying of ZnO into SnO leads to a change of the valence state of the tin from Sn 0 via Sn 2+ to Sn 4+, which can be counteracted by reducing the oxygen partial pressuremore » during the deposition. The optical characterization of the smooth <10 at. % Sn 1-xZn xO thin films showed an increase in the absorption coefficient in the range from 1 to 2 eV, which is consistent with the theoretical predictions for the isovalent alloying. However, the experimentally observed alloying effect may be convoluted with the effect of local variations of the Sn oxidation state. As a result, this effect would have to be minimized to improve the (Sn,Zn)O optical and electrical properties for their use as absorbers in solar energy conversion applications.« less

Structural Inheritance and Redox Performance of Nanoporous Electrodes from Nanocrystalline Fe85.2B10-14P0-4Cu0.8 Alloys

PubMed Central

Fu, Chaoqun; Xu, Lijun; Dan, Zhenhua; Makino, Akihiro; Hara, Nobuyoshi; Qin, Fengxiang; Chang, Hui

2017-01-01

Nanoporous electrodes have been fabricated by selectively dissolving the less noble α-Fe crystalline phase from nanocrystalline Fe85.2B14–xPxCu0.8 alloys (x= 0, 2, 4 at.%). The preferential dissolution is triggered by the weaker electrochemical stability of α-Fe nanocrystals than amorphous phase. The final nanoporous structure is mainly composed of amorphous residual phase and minor undissolved α-Fe crystals and can be predicted from initial microstructure of nanocrystalline precursor alloys. The structural inheritance is proved by the similarity of the size and outlines between nanopores formed after dealloying in 0.1 M H2SO4 and α-Fe nanocrystals precipitated after annealing of amorphous Fe85.2B14−xPxCu0.8 (x = 0, 2, 4 at.%) alloys. The Redox peak current density of the nanoporous electrodes obtained from nanocrystalline Fe85.2B10P4Cu0.8 alloys is more than one order higher than those of Fe plate electrode and its counterpart nanocrystalline alloys due to the large surface area and nearly-amorphous nature of ligaments. PMID:28594378

Microwave assisted combustion synthesis of nanocrystalline CoFe2O4 for LPG sensing

NASA Astrophysics Data System (ADS)

Chaudhari, Prashant; Acharya, S. A.; Darunkar, S. S.; Gaikwad, V. M.

2015-08-01

A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe2O4. The process takes only a few minutes to obtain as-synthesized CoFe2O4. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe2O4 prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe2O4 thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

Effect of annealing temperature on optical and electrical properties of ZrO2-SnO2 based nanocomposite thin films

NASA Astrophysics Data System (ADS)

Anitha, V. S.; Lekshmy, S. Sujatha; Berlin, I. John; Joy, K.

2014-01-01

Transparent nanocomposite ZrO2-SnO2 thin films were prepared by sol-gel dip-coating technique. Films were annealed at 500°C, 800°C and 1200°C respectively. X-ray diffraction(XRD) spectra showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. The grain size of all the three phases' increased with annealing temperature. An average transmittance greater than 85%(in UV-Visible region) is observed for all the films. The band gap for the films decreased from 4.79 eV to 4.62 eV with increase in annealing temperature from 500 to 1200 °C. The electrical resistivity increased with increase in annealing temperature. Such composite ZrO2-SnO2 films can be used in many applications and in optoelectronic devices.

Ant-cave structured MnCO3/Mn3O4 microcubes by biopolymer-assisted facile synthesis for high-performance pseudocapacitors

NASA Astrophysics Data System (ADS)

Chandra Sekhar, S.; Nagaraju, Goli; Yu, Jae Su

2018-03-01

Porous and ant-cave structured MnCO3/Mn3O4 microcubes (MCs) were facilely synthesized via a biopolymer-assisted hydrothermal approach. Herein, chitosan was used as a natural biopolymer, which greatly controls the surface morphology and size of the prepared composite. The amino and hydroxyl group-functionalized chitosan engraves the outer surface of MCs during the hydrothermal process, which designs the interesting morphology of nanopath ways on the surface of MCs. When used as an electrode material for pseudocapacitors, the ant-cave structured MnCO3/Mn3O4 MCs showed superior energy storage values compared to the material prepared without chitosan in aqueous electrolyte solution. Precisely, the prepared ant-cave structured MnCO3/Mn3O4 MCs exhibited a maximum specific capacitance of 116.2 F/g at a current density of 0.7 A/g with an excellent cycling stability of 73.86% after 2000 cycles. Such facile and low-cost synthesis of pseudocapacitive materials with porous nanopaths is favorable for the fabrication of high-performance energy storage devices.

Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

2014-02-01

SnO2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO2, were investigated. The particle size (1.8-16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO2 single-phase structure for samples annealed at 1073-1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

Popcorn balls-like ZnFe2O4-ZrO2 microsphere for photocatalytic degradation of 2,4-dinitrophenol

NASA Astrophysics Data System (ADS)

Chen, Xi; Liu, Yutang; Xia, Xinnian; Wang, Longlu

2017-06-01

In this paper, novel popcorn balls-like ZnFe2O4-ZrO2 composite microspheres were successfully fabricated by a simple hydrothermal method. The morphology, structure and optical property of the microspheres were characterized. The microspheres were used as the photocatalysts to degrade 2,4-dinitrophenol, and exhibited superior photocatalytic performance. Under simulated solar visible light irradiation, the degradation rate of ZnFe2O4-ZrO2 photocatalyst (mass ratio of ZnFe2O4/ZrO2 = 2:1) was almost 7.4 and 2.4 times higher than those of pure ZnFe2O4 and ZrO2. The enhancement could attribute to stronger light absorption, lower carrier recombination and multi-porous structure of the microspheres. Moreover, the popcorn balls-like photocatalysts can be easily separated, because of the magnetism of the samples. After five times runs, the photocatalyst still showed 90% of its photocatalytic degradation efficiency. This work demonstrated a good prospect for removing organic pollutants in water.

Magnetic micro scavengers: highly porous Ni1‑x Co x Fe2O4 microcubes for efficient disintegration of nitrophenol

NASA Astrophysics Data System (ADS)

Pervaiz, Erum; Syam Azhar Virk, Muhammad; Tareen, Ayesha Khan; Zhang, Bingxue; Zhao, Qiuyan; Wang, Zhenzhen; Yang, Minghui

2018-05-01

The fabrication of functional materials in patterned morphology is focused to obtain remarkable physiognomies of the materials for certain applications. Instead of randomly distributed agglomerated nanoparticles, it is highly desirable to arrange them in a motif, as this directed formation of nanomaterials can have a substantial influence on their performance and activity in various applications. With this perspective, MOF derived hollow cubes of nickel cobalt ferrites have been synthesized via a facile process using sacrificial templates at 600 °C. Microcubes, composed of tiny grains in a size range from 10 nm ± 2 nm were obtained in pure form as a polycrystalline material. The high specific surface area (1185 m2 g‑1) and mesoporous nature of hollow cubic ferrites were found to be excellent adsorbents for nitrophenol at room temperature. The equilibrium quantity of adsorbed nitrophenol was calculated as 47 mg g‑1 ferrite, accomplished in 7 min. Their large surface area, mesopores and hollow nature, in combination with controlled size distribution of grains, have enabled this remarkable utilization of nanoferrites for removal of nitrophenol from water.

Selective Improvement of NO2 Gas Sensing Behavior in SnO2 Nanowires by Ion-Beam Irradiation.

PubMed

Kwon, Yong Jung; Kang, Sung Yong; Wu, Ping; Peng, Yuan; Kim, Sang Sub; Kim, Hyoun Woo

2016-06-01

We irradiated SnO2 nanowires with He ions (45 MeV) with different ion fluences. Structure and morphology of the SnO2 nanowires did not undergo noticeable changes upon ion-beam irradiation. Chemical equilibrium in SnO2/gas systems was calculated from thermodynamic principles, which were used to study the sensing selectivity of the tested gases, demonstrating the selective sensitivity of the SnO2 surface to NO2 gas. Being different from other gases, including H2, ethanol, acetone, SO2, and NH3, the sensor response to NO2 gas significantly increases as the ion fluence increases, showing a maximum under an ion fluence of 1 × 10(16) ions/cm(2). Photoluminescence analysis shows that the relative intensity of the peak at 2.1 eV to the peak at 2.5 eV increases upon ion-beam irradiation, suggesting that structural defects and/or tin interstitials have been generated. X-ray photoelectron spectroscopy indicated that the ionic ratio of Sn(2+/)Sn(4+) increases by the ion-beam irradiation, supporting the formation of surface Sn interstitials. Using thermodynamic calculations, we explained the observed selective sensing behavior. A molecular level model was also established for the adsorption of NO2 on ion-irradiated SnO2 (110) surfaces. We propose that the adsorption of NO2-related species is considerably enhanced by the generation of surface defects that are comprised of Sn interstitials.

Contrasting the material chemistry of Cu 2ZnSnSe 4 and Cu 2ZnSnS (4-x)Se x

DOE PAGES

Aguiar, Jeffery A.; Patel, Maulik; Aoki, Toshihiro; ...

2016-02-02

Earth-abundant sustainable inorganic thin-film solar cells, independent of precious elements, pivot on a marginal material phase space targeting specific compounds. Advanced materials characterization efforts are necessary to expose the roles of microstructure, chemistry, and interfaces. Here, the earth-abundant solar cell device, Cu 2ZnSnS (4-x)Se x, is reported, which shows a high abundance of secondary phases compared to similarly grown Cu 2ZnSnSe 4.

The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C

NASA Astrophysics Data System (ADS)

Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko

1990-05-01

The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C are determined by means of a classical quenching method. There are a series of homologous solid solutions, In 1.28Fe 0.72O 3(ZnO)InFeO 3(ZnO), In 1.69Fe 0.31O 3(ZnO) 2InFeO 3(ZnO) 2In 0.85Fe 1.15O 3(ZnO) 2, In 2O 3(ZnO) 3InFeO 3(ZnO) 3In 0.78Fe 1.22O 3(ZnO) 3, In 2O 3(ZnO) 4InFeO 3(ZnO) 4In 0.62Fe 1.38O 3(ZnO) 4, In 2O 3(ZnO) 5InFeO 3(ZnO) 5In 0.67Fe 1.33O 3(ZnO) 5, In 2O 3(ZnO) 6InFeO 3(ZnO) 6In 0.60Fe 1.40O 3(ZnO) 6, In 2O 3(ZnO) 7InFeO 3(ZnO) 7In 0.51Fe 1.49O 3(ZnO) 7, In 2O 3(ZnO) 8InFeO 3(ZnO) 8In 1- xFe 1+ xO 3(ZnO) 8 (0.44 ≦ x ≦ 0.64), In 2O 3(ZnO) 9InFeO 3(ZnO) 9In 0.20Fe 1.80O 3(ZnO) 9, In 2O 3(ZnO) 10InFeO 3(ZnO) 10In 1- xFe 1+ xO 3(ZnO) 10 (0.74 ≦ x ≦ 0.89), In 2O 3(ZnO) 11InFeO 3(ZnO) 11In 1- xFe 1+ xO 3(ZnO) 11 (0.60 ≦ x < 1.00), and In 2O 3(ZnO) 13InFeO 3(ZnO) 13Fe 2O 3(ZnO) 13 having the layered structures with space group R overline3m (m = odd) or {P6 3}/{mmc} (m = even) for m in the InFeO 3(ZnO) m. We conclude that there are a series of homologous phases, (Fe 2O 3)(ZnO) m (m ≧ 12) , in the binary ZnOFe 2O 3 system. The lattice constants for these solid solutions are presented as a hexagonal crystal system. It is also concluded that the crystal structures for each solid solution consist of three kinds of layers which are stacked perpendicular to the c-axis in the hexagonal crystal system. In 1+ xFe 1- xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of the InO 1.5, (In xFe 1- xZn)O 2.5, and ZnO layers, and In 1- xFe 1+ xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of (In 1- xFe x)O 1.5, (FeZn)O 2.5, and ZnO layers, respectively. The solid solution range between Fe 2ZnO 4 and In xFe 2- xZnO 4 ( x = 0.40 ± 0.02) with a spinel structure is observed.

Facile fabrication of robust TiO2@SnO2@C hollow nanobelts for outstanding lithium storage

NASA Astrophysics Data System (ADS)

Tian, Qinghua; Li, Lingxiangyu; Chen, Jizhang; Yang, Li; Hirano, Shin-ichi

2018-02-01

Elaborate fabrication of state-of-the-art nanostructure SnO2@C-based composites greatly contributes to alleviate the huge volume expansion issue of the SnO2 anodes. But the preparation processes of most of them are complicated and tedious, which is generally adverse to the development of SnO2@C-based composite anodes. Herein, a unique nanostructure of TiO2@SnO2@C hollow nanobelts (TiO2@SnO2@C HNBs), including the characteristics of one-dimensional architecture, sandwich protection, hollow structure, carbon coating, and a mechanically robust TiO2 support, has been fabricated by a facile approach for the first time. As anodes for lithium-ion batteries, the as-fabricated TiO2@SnO2@C HNBs exhibit an outstanding lithium storage performance, delivering capacity of 804.6 and 384. 5 mAh g-1 at 200 and even 1000 mA g-1 after 500 cycles, respectively. It is demonstrated that thus outstanding performance is mainly attributed to the unique nanostructure of TiO2@SnO2@C HNBs.

Synthesis and Characterization of Photocatalytic TiO 2 -ZnFe 2 O 4 Nanoparticles

DOE PAGES

Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

2006-01-01

A new coprecipimore » tation/hydrolysis synthesis route is used to create a TiO 2 -ZnFe 2 O 4 nanocomposite that is directed towards extending the photoresponse of TiO 2 from UV to visible wavelengths ( > 400   nm ). The effect of TiO 2 's accelerated anatase-rutile phase transformation due to the presence of the coupled ZnFe 2 O 4 narrow-bandgap semiconductor is evaluated. The transformation's dependence on pH, calcinations temperature, particle size, and ZnFe 2 O 4 concentration has been analyzed using XRD, SEM, and UV-visible spectrometry. The requirements for retaining the highly photoactive anatase phase present in a ZnFe 2 O 4 nanocomposite are outlined. The visible-light-activated photocatalytic activity of the TiO 2 -ZnFe 2 O 4 nanocomposites has been compared to an Aldrich TiO 2 reference catalyst, using a solar-simulated photoreactor for the degradation of phenol.« less

Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Cheng, Hsyi-En; Lin, Chun-Yuan; Hsu, Ching-Ming

2017-02-01

Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

Highly enhanced ultraviolet photosensitivity and recovery speed in electrospun Ni-doped SnO2 nanobelts

NASA Astrophysics Data System (ADS)

Huang, Siya; Matsubara, Kohei; Cheng, Jing; Li, Heping; Pan, Wei

2013-09-01

Precisely controlled Ni-doped SnO2 (NSO) nanobelt arrays are synthesized and assembled via electrospinning. In comparison to pristine SnO2 nanobelts, enhanced photosensitivity (˜103) as well as recovery speed (˜1 s) is obtained in NSO nanobelts. The mechanism is clarified by the compensation effect of acceptor impurity Ni, which not only promotes the oxygen-surface interaction but also introduces trapping centers in SnO2 matrix. The reduced grain size (˜4 nm) along with increased depletion layer thickness also benefits the photosensitivity of NSO nanobelts. These improved photoresponse properties make the NSO nanobelt a promising candidate for high-performance ultraviolet detectors.

Hierarchical MnO2/SnO2 heterostructures for a novel free-standing ternary thermite membrane.

PubMed

Yang, Yong; Zhang, Zhi-Cheng; Wang, Peng-Peng; Zhang, Jing-Chao; Nosheen, Farhat; Zhuang, Jing; Wang, Xun

2013-08-19

We report the synthesis of a novel hierarchical MnO2/SnO2 heterostructures via a hydrothermal method. Secondary SnO2 nanostructure grows epitaxially on the surface of MnO2 backbones without any surfactant, which relies on the minimization of surface energy and interfacial lattice mismatch. Detailed investigations reveal that the cover density and morphology of the SnO2 nanostructure can be tailored by changing the experimental parameter. Moreover, we demonstrate a bottom-up method to produce energetic nanocomposites by assembling nanoaluminum (n-Al) and MnO2/SnO2 hierarchical nanostructures into a free-standing MnO2/SnO2/n-Al ternary thermite membrane. This assembled approach can significantly reduce diffusion distances and increase their intimacy between the components. Different thermite mixtures were investigated to evaluate the corresponding activation energies using DSC techniques. The energy performance of the ternary thermite membrane can be manipulated through different components of the MnO2/SnO2 heterostructures. Overall, our work may open a new route for new energetic materials.

Magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles for visible light photodegradation of methyl orange

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulkarni, Suresh D., E-mail: suresh.dk@manipal.edu; Kumbar, Sagar; Menon, Samvit G.

Highlights: • Phase pure, magnetic ZnFe{sub 2}O{sub 4}@ZnO nanoparticles synthesized with excellent yield. • ZnFe{sub 2}O{sub 4}@ZnO displayed higher UV photocatalytic efficiency than ZnO nanoparticles. • First report on visible light photodegradation of methyl orange by ZnFe{sub 2}O{sub 4}@ZnO. • Excellent reusability of ZnFe{sub 2}O{sub 4}@ZnO nanoparticles observed for azo dye removal. - Abstract: Visible light photodegradation of aqueous methyl orange using magnetically separable core–shell ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported. A combination of low temperature (190 °C) microwave synthesis and hydrothermal method were used to prepare phase pure material with excellent yield (95%). The magnetic separability, surface area ofmore » 41 m{sup 2}/g and visible light absorption make ZnFe{sub 2}O{sub 4}@ZnO nanoparticles a good solar photocatalyst. ZnFe{sub 2}O{sub 4}@ZnO displayed greater UV photocatalytic efficiency than ZnO owing to the generation of large number of electron-hole pairs. Visible light photodegradation of MO using ZnFe{sub 2}O{sub 4}@ZnO nanoparticles is reported for the first time. Higher first order rate constants under both UV and visible light for core-shell nanoparticles suggested their superiority over its individual oxides. The ZnFe{sub 2}O{sub 4}@ZnO showed excellent reusability with high photocatalytic efficiencies suggesting its suitability for solar photocatalytic applications.« less

Enhanced antibacterial performance of hybrid semiconductor nanomaterials: ZnO/SnO 2 nanocomposite thin films

NASA Astrophysics Data System (ADS)

Talebian, Nasrin; Nilforoushan, Mohammad Reza; Zargar, Elahe Badri

2011-10-01

The nano-sized coupled oxides ZnO/SnO 2 thin films in a molar ratio of 2:1 (Z2S), 1:1 (ZS) and 1:2 (ZS2) were prepared using sol-gel dip coating method and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. Escherichia coli ( E. coli, ATCC 25922) was selected as a model for the Gram-negative bacteria to evaluate antibacterial property of composite samples compared with single ZnO (Z) and single SnO 2 (S) films. The antibacterial activity has been studied applying the so-called antibacterial drop test under UV illumination. The bactericidal activity was estimated by relative number of bacteria survived calculated from the number of viable cells which form colonies on the nutrient agar plates. The influence of the SnO 2-ZnO nanocomposite composition on the structural features and on the antibacterial properties of the thin films are reported and discussed. It is found that all coatings exhibited a high antibacterial activity. The coupled oxide photocatalyst Z2S has better photocatalytic activity to bacteria inactivation than ZS, ZS2, Z and S films. Furthermore, nanostructured films were active even in the absence of irradiation.

The luminescence properties of nanocrystalline phosphors Mg2SiO4:Eu3+

NASA Astrophysics Data System (ADS)

Kolomytsev, A. Y.; Mamonova, D. V.; Manshina, A. A.; Kolesnikov, I. E.

2017-11-01

Nanocrystalline Eu3+-doped Mg2SiO4 powders were prepared with combined Pechini-solid phase synthesis. The structural properties were investigated with XRD, SEM and Raman spectroscopy. XRD pattern indicated that Mg2SiO4:Eu3+ were obtained with formation of other phase: MgO. Raman spectrum revealed good homogeneity and crystallinity of synthesized nanopowders. The luminescence properties were studied with measurement of excitation and emission spectra and decay curves. The effect of Eu3+ concentration on 5D0 level lifetime was studied. Most probably, the observed shortening of 5D0 level lifetime with Eu3+ concentration is caused by increase of nonradiative process probability.

Photocurrent generation in SnO2 thin film by surface charged chemisorption O ions

NASA Astrophysics Data System (ADS)

Lee, Po-Ming; Liao, Ching-Han; Lin, Chia-Hua; Liu, Cheng-Yi

2018-06-01

We report a photocurrent generation mechanism in the SnO2 thin film surface layer by the charged chemisorption O ions on the SnO2 thin film surface induced by O2-annealing. A critical build-in electric field in the SnO2 surface layer resulted from the charged O ions on SnO2 surface prolongs the lifetime and reduces the recombination probability of the photo-excited electron-hole pairs by UV-laser irradiation (266 nm) in the SnO2 surface layer, which is the key for the photocurrent generation in the SnO2 thin film surface layer. The critical lifetime of prolonged photo-excited electron-hole pair is calculated to be 8.3 ms.

Self-cleaning antimicrobial surfaces by bio-enabled growth of SnO2 coatings on glass

NASA Astrophysics Data System (ADS)

André, Rute; Natalio, Filipe; Tahir, Muhammad Nawaz; Berger, Rüdiger; Tremel, Wolfgang

2013-03-01

photoactivity - creates a self-cleaning surface. The intrinsic self-cleaning properties could lead to the development of new protective, antifouling coatings on various substrates. Electronic supplementary information (ESI) available: (1) QCM measurement of SnO2 deposition on spermine functionalized silica-based sensors, (2) scheme of the surface functionalization procedure, (3) FTIR-ATR analysis of polyamine (spermine) functionalized glass surfaces, (4) FITC staining of amine groups on glass surfaces, (5) AFM height analysis of bare, spermine coated and SnO2 coated glass slides, (6) SEM micrograph of a spermine functionalized SnO2 coated glass slide, (7) XPS analysis of SnO2 coated surfaces, (8) kinetic profile of rhodamine B degradation with spermine/SnO2, (9) control experiments for the photodegradation of rhodamine B, (10) comparison with commercial SnO2 catalyst, (11) incubation of non-functionalized glass surfaces with E. coli, and (12) incubation of SnO2 coated glass surfaces with E. coli. See DOI: 10.1039/c3nr00007a

Microstructural, Optical and Dielectric Properties of Al-Incorporated SnO2 Nanoparticles

NASA Astrophysics Data System (ADS)

Ahmed, Ateeq; Tripathi, P.; Naseem Siddique, M.; Ali, Tinku

2017-08-01

In this work, Pure SnO2 and Al doped SnO2 nanoparticles with the composition Sn1-xAlxO2 (x = 0, and 0.05) have been successfully prepared using sol-gel technique. The effect of Al dopant on microstructural, optical and dielectric properties has been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet (UV-Visible) absorption spectroscopy andImpedance spectroscopy (LCR meter)respectively. The XRD patterns indicated tetragonal rutile structure with single phase without any detectable impurity for all samples and incorporation of Al ions into the SnO2 lattice. Crystalline size decreased with aluminum content. The results of SEM confirm nanoparticles size decreases with Al dopant. UV-Visible results showed that optical band also decreases when Al is doped into pure SnO2 lattice. Frequency dependent dielectric properties of pure and doped SnO2 nanoparticles have been also studied.

Shape Engineering Driven by Selective Growth of SnO2 on Doped Ga2O3 Nanowires.

PubMed

Alonso-Orts, Manuel; Sánchez, Ana M; Hindmarsh, Steven A; López, Iñaki; Nogales, Emilio; Piqueras, Javier; Méndez, Bianchi

2017-01-11

Tailoring the shape of complex nanostructures requires control of the growth process. In this work, we report on the selective growth of nanostructured tin oxide on gallium oxide nanowires leading to the formation of SnO 2 /Ga 2 O 3 complex nanostructures. Ga 2 O 3 nanowires decorated with either crossing SnO 2 nanowires or SnO 2 particles have been obtained in a single step treatment by thermal evaporation. The reason for this dual behavior is related to the growth direction of trunk Ga 2 O 3 nanowires. Ga 2 O 3 nanowires grown along the [001] direction favor the formation of crossing SnO 2 nanowires. Alternatively, SnO 2 forms rhombohedral particles on [110] Ga 2 O 3 nanowires leading to skewer-like structures. These complex oxide structures were grown by a catalyst-free vapor-solid process. When pure Ga and tin oxide were used as source materials and compacted powders of Ga 2 O 3 acted as substrates, [110] Ga 2 O 3 nanowires grow preferentially. High-resolution transmission electron microscopy analysis reveals epitaxial relationship lattice matching between the Ga 2 O 3 axis and SnO 2 particles, forming skewer-like structures. The addition of chromium oxide to the source materials modifies the growth direction of the trunk Ga 2 O 3 nanowires, growing along the [001], with crossing SnO 2 wires. The SnO 2 /Ga 2 O 3 junctions does not meet the lattice matching condition, forming a grain boundary. The electronic and optical properties have been studied by XPS and CL with high spatial resolution, enabling us to get both local chemical and electronic information on the surface in both type of structures. The results will allow tuning optical and electronic properties of oxide complex nanostructures locally as a function of the orientation. In particular, we report a dependence of the visible CL emission of SnO 2 on its particular shape. Orange emission dominates in SnO 2 /Ga 2 O 3 crossing wires while green-blue emission is observed in SnO 2 particles attached to Ga 2

Low-loss Z-type barium hexaferrite composites from nanoscale ZnAl2O4 addition for high-frequency applications

NASA Astrophysics Data System (ADS)

Zheng, Zongliang; Feng, Quanyuan; Harris, Vincent G.

2018-05-01

In this study, nanocrystalline ZnAl2O4 (ZA) were introduced to Z-type barium hexaferrite (Co2Z) and the effects of ZA addition upon the crystal-phase composition, microstructure, permeability and permittivity as well as losses characteristics over a wide frequency range of 10 MHz-1 GHz have been systematically investigated. With increasing ZA content (x) from 0 to 15 wt%, the permeability μ' at low frequencies decreased from 12.0 to 4.3, while the permittivity ɛ' was decreased from 27.4 to 10.7. Correspondingly, the frequency stability of permeability and permittivity were improved and the losses were effectively reduced. When x is in the range of 5-10 wt%, the magnetic loss tan δμ is in the order of 10-2 and the dielectric loss tan δɛ is in the order of 10-3 at 300 MHz, which is lower by one order of magnitude compared with that of undoped Co2Z. The modified magnetic and dielectric properties are closely related to the changing phase composition and microstructure.

Microwave-Hydrothermal Synthesis of SnO2-CNTs Hybrid Nanocomposites with Visible Light Photocatalytic Activity.

PubMed

Wu, Shuisheng; Dai, Weili

2017-03-03

SnO2 nanoparticles coated on carbon nanotubes (CNTs) were prepared via a simple microwave-hydrothermal route. The as-obtained SnO2-CNTs composites were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The photocatalytic activity of as-prepared SnO2-CNTs for degradation of Rhodamine B under visible light irradiation was investigated. The results show that SnO2-CNTs nanocomposites have a higher photocatalytic activity than pure SnO2 due to the rapid transferring of electrons and the effective separation of holes and electrons on SnO2-CNTs.

Microwave-Hydrothermal Synthesis of SnO2-CNTs Hybrid Nanocomposites with Visible Light Photocatalytic Activity

PubMed Central

Wu, Shuisheng; Dai, Weili

2017-01-01

SnO2 nanoparticles coated on carbon nanotubes (CNTs) were prepared via a simple microwave-hydrothermal route. The as-obtained SnO2-CNTs composites were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The photocatalytic activity of as-prepared SnO2-CNTs for degradation of Rhodamine B under visible light irradiation was investigated. The results show that SnO2-CNTs nanocomposites have a higher photocatalytic activity than pure SnO2 due to the rapid transferring of electrons and the effective separation of holes and electrons on SnO2-CNTs. PMID:28336888

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals.

PubMed

Mao, Xiaoli; Zhou, Ru; Zhang, Shouwei; Ding, Liping; Wan, Lei; Qin, Shengxian; Chen, Zhesheng; Xu, Jinzhang; Miao, Shiding

2016-01-13

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs.

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals

PubMed Central

Mao, Xiaoli; Zhou, Ru; Zhang, Shouwei; Ding, Liping; Wan, Lei; Qin, Shengxian; Chen, Zhesheng; Xu, Jinzhang; Miao, Shiding

2016-01-01

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs. PMID:26758941

Nanofibrillated Cellulose-Assisted Synthesis of Fiber-Like ZnO-ZnFe2O4 Composites with Enhanced Visible-Light-Driven Photocatalytic Activity

NASA Astrophysics Data System (ADS)

Cai, Aijun; Guo, Aiying; Du, Liqiang; Chang, Yongfang; Wang, Xiuping

2018-05-01

In this article, fiber-like ZnO-ZnFe2O4 composites are obtained by using nanofibrillated cellulose as a biotemplate. The as-prepared composites exhibit strong absorbance in the visible-light region. The ZnO-ZnFe2O4 composites exhibit a similar bandgap (1.88 eV) compared with the ZnFe2O4 (1.85 eV). The ZnO-ZnFe2O4 composites can be easily collected by an external magnet, which contributes to improving the utilization efficiency of the photocatalysts. The photocatalytic activity of the ZnO-ZnFe2O4 catalysts was evaluated by photodegrading rhodamine B (RhB) under visible-light irradiation. Compared with ZnO and ZnFe2O4, the ZnO-ZnFe2O4 catalysts show higher photocatalytic activity due to the efficient electron-hole separation.

Detection of Cu2Zn5SnSe8 and Cu2Zn6SnSe9 phases in co-evaporated Cu2ZnSnSe4 thin-films

NASA Astrophysics Data System (ADS)

Schwarz, Torsten; Marques, Miguel A. L.; Botti, Silvana; Mousel, Marina; Redinger, Alex; Siebentritt, Susanne; Cojocaru-Mirédin, Oana; Raabe, Dierk; Choi, Pyuck-Pa

2015-10-01

Cu2ZnSnSe4 thin-films for photovoltaic applications are investigated using combined atom probe tomography and ab initio density functional theory. The atom probe studies reveal nano-sized grains of Cu2Zn5SnSe8 and Cu2Zn6SnSe9 composition, which cannot be assigned to any known phase reported in the literature. Both phases are considered to be metastable, as density functional theory calculations yield positive energy differences with respect to the decomposition into Cu2ZnSnSe4 and ZnSe. Among the conceivable crystal structures for both phases, a distorted zinc-blende structure shows the lowest energy, which is a few tens of meV below the energy of a wurtzite structure. A band gap of 1.1 eV is calculated for both the Cu2Zn5SnSe8 and Cu2Zn6SnSe9 phases. Possible effects of these phases on solar cell performance are discussed.

Structure and properties of hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O

NASA Astrophysics Data System (ADS)

Haussühl, S.; Middendorf, B.; Dörffel, M.

1991-07-01

Mg-hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O were prepared by crystallization from hot aqueous solutions (70°C). The structure of (Mg 0.206Zn 0.794) 3(PO 4) 2 · 4H 2O has been determined from 1612 unique reflections (MoKα, R = 0.033): Pnma, a1 = 10.594(2), a2 = 18.333(2), a3 = 5.029(2)Å, Z = 4, Dcalc = 2.943g cm -3. The structure resembles that of pure hopeite. However, the magnesium atoms occupy only the sixcoordinated site. The thermal behavior of hopeites is strongly influenced by the substitution of Zn by Mg. The dehydration range is shifted to higher temperatures with increasing Mg content. A strongly anisotropic thermal expansion was measured by X-ray diffraction in a temperature range of -40° to 50°C. Experiments to substitute Zn by Ca, Sr, and Ba in the hopeite failed. A hitherto unknown monoclinic phase with the composition BaZn 2(PO 4) 2 · H 2O and a1 = 4.707(2), a2 = 7.840(2), a3 = 8.061(3)Å, and α 2 = 88.99(4)° was found.

Structure and magnetic properties of amorphous and nanocrystalline Fe 40Co 40Cu 0.5Zr 9Al 2Si 4B 4.5 alloys

NASA Astrophysics Data System (ADS)

Mitra, A.; Kim, H.-Y.; Louzguine, D. V.; Nishiyama, N.; Shen, B.; Inoue, A.

2004-07-01

Crystallisation behaviour and magnetic properties of as-spun and annealed Fe 40Co 40Cu 0.5Zr 9Al 2Si 4B 4.5 alloy have been studied. The annealing was performed at 873 K for 15 min. XRD and TEM studies shows the formation of nanocrystalline α-(Fe,Co)(SiAl) particles with 7.5±2 nm in diameter dispersed in an amorphous matrix. The Curie temperature of the as-spun amorphous ribbon is 736 K. Saturation magnetisation of the annealed sample decreases at a rate of 0.5 emu/g/K in the measured temperature range of 300-1000 K. Excellent room temperature AC magnetic properties are achieved for the nanocrystalline sample. The low value of the imaginary part of the permeability and the high cut-off frequency (20 kHz) suggest that the eddy current contribution in the annealed materials is low. The coercivity of the annealed sample remains almost constant at 95 A/m up to the frequency of 20 kHz. High saturation magnetisation, high Curie temperature and excellent soft magnetic properties in the nanocrystalline state suggests that Fe 40Co 40Cu 0.5Zr 9Al 2Si 4B 4.5 alloy is a strong candidate for high temperature magnetic application.

Ion beam induced amorphization and bond breaking in Zn2SiO4:Eu3+ nanocrystalline phosphor.

PubMed

Sunitha, D V; Nagabhushana, H; Singh, Fouran; Sharma, S C; Dhananjaya, N; Nagabhushana, B M; Chakradhar, R P S

2012-05-01

This paper reports on the ionoluminescence (IL) of Zn(2)SiO(4):Eu(3+) nanophosphors bombarded with 100 MeV Si(7+) ions with fluences in the range (3.91-21.48)×10(12) ions cm(-2). The prominent IL emission peaks recorded at 580, 590, 612, 650 and 705 nm are attributed to the luminescence centers activated by Eu(3+) ions. It is observed that IL intensity decreases and saturates with increase of Si(7+) ion fluence. Fourier transform infrared (FT-IR) studies confirm surface/bulk amorphization for a fluence of (3.91-21.48)×10(13) ions cm(-2). These results show degradation of SiO (2ν(3)) bonds present on the surface of the sample and/or due to lattice disorder produced by dense electronic excitation under heavy ion irradiation. These results are discussed in detail. Copyright © 2011 Elsevier B.V. All rights reserved.

Adsorption of Cd2+ ions on plant mediated SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Haq, Sirajul; Rehman, Wajid; Waseem, Muhammad; Shahid, Muhammad; Mahfooz-ur-Rehman; Hussain Shah, Khizar; Nawaz, Mohsan

2016-10-01

Plant mediated SnO2 nanoparticles were synthesized by using SnCl4.5H2O as a precursor material. The nanoparticles were then characterized for BET surface area measurements, energy dispersive x-rays (EDX), scanning electron microscopy (SEM), UV-vis diffuse reflectance (DRS) spectra and x-rays diffraction (XRD) analysis. The successful synthesis of SnO2 nanoparticles was confirmed by EDX analysis. The particle sizes were in the range 19-27 nm whereas the crystallite size computed from XRD measurement was found to be 19.9 nm. Batch adsorption technique was employed for the removal of Cd2+ ions from aqueous solution. The sorption studies of Cd2+ ions were performed at pHs 4 and 6. The equilibrium concentration of Cd2+ ions was determined by atomic absorption spectrometer (flame mode). The uptake of Cd2+ ions was affected by initial concentration, pH and temperature of the electrolytic solution. It was observed that the adsorption of Cd2+ ions enhanced with increase in the initial concentration of Cd2+ ions whereas a decrease in the percent adsorption was detected. From the thermodynamic parameters, the adsorption process was found spontaneous and endothermic in nature. The n values confirmed 2:1 exchange mechanism between surface protons and Cd2+ ions.

Two new three-dimensional zinc phosphites templated by piperazine: [H2pip][Zn3(HPO3)4(H2O)2] and K[H2pip]0.5[Zn3(HPO3)4

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Wang, Guo-Ming; Wang, Zong-Hua; Wang, Ying-Xia; Lin, Jian-Hua

2014-01-01

Two three-dimensional open-framework zinc phosphites with the same organically templated, [H2pip][Zn3(HPO3)4(H2O)2] (1) and K[H2pip]0.5[Zn3(HPO3)4] (2) (pip = piperazine), have been solvothermally synthesized and structurally characterized by IR, elemental analysis, thermogravimetric analysis, powder and single-crystal X-ray diffractions. Compound 1 consists of ZnO4 tetrahedra, [HPO3] pseudopyramids and [ZnO4(H2O)2] octahedra, which are linked through their vertexes to generate three-dimensional architecture with intersecting 8-membered channels along the [1 0 0], [0 0 1] and [1 0 1] directions. Compound 2 is constructed from strictly alternating ZnO4 tetrahedra and [HPO3] pseudopyramids, and exhibits (3,4)-connected inorganic framework with 8-, and 12-membered channels, in which the K+ and diprotonated H2pip2+ extra-framework cations reside, respectively. The coexistence of inorganic K+ and organic piperazine mixed templates in the structure is unique and, to the best of our knowledge, firstly observed in metal-phosphite materials. In addition, the participation of left-handed and right-handed helical chains in construction of the puckered 4.82 sheet structure in 2 is also noteworthy.

Structural and electrochemical analysis of chemically synthesized microcubic architectured lead selenide thin films

NASA Astrophysics Data System (ADS)

Bhat, T. S.; Shinde, A. V.; Devan, R. S.; Teli, A. M.; Ma, Y. R.; Kim, J. H.; Patil, P. S.

2018-01-01

The present work deals with the synthesis of lead selenide (PbSe) thin films by simple and cost-effective chemical bath deposition method with variation in deposition time. The structural, morphological, and electrochemical properties of as-deposited thin films were examined using characterization techniques such as X-ray diffraction spectroscopy (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy. XRD reveals formation of rock salt phase cubic structured PbSe. FE-SEM images show the formation of microcubic structured morphology. The existence of the PbSe is confirmed from the XPS analysis. On the other hand, CV curves show four reaction peaks corresponding to oxidation [PbSe and Pb(OH)2] and reduction (PbO2 and Pb(OH)2) at the surface of PbSe thin films. The PbSe:2 sample deposited for 80 min. shows maximum specific capacitance of 454 ± 5 F g- 1 obtained at 0.25 mA cm- 2 current density. The maximum energy density of 69 Wh kg- 1 was showed by PbSe:2 electrode with a power density of 1077 W kg- 1. Furthermore, electrochemical impedance studies of PbSe:2 thin film show 80 ± 3% cycling stability even after 500 CV cycles. Such results show the importance of microcubic structured PbSe thin film as an anode in supercapacitor devices.

Photoluminescence analysis of Ce{sup 3+}:Zn{sub 2}SiO{sub 4} & Li{sup +}+ Ce{sup 3+}:Zn{sub 2}SiO{sub 4}: phosphors by a sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babu, B. Chandra, E-mail: chandrababuphd@gmail.com; Vandana, C. Sai; Guravamma, J.

2015-06-24

Here, we report on the development and photoluminescence analysis of Zn{sub 2}SiO{sub 4}, Ce{sup 3+}:Zn{sub 2}SiO{sub 4} & Li{sup +} + Ce{sup 3+}: Zn{sub 2}SiO{sub 4} novel powder phosphors prepared by a sol-gel technique. The total amount of Ce{sup 3+} ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn{sub 2}SiO{sub 4}) and Ce{sup 3+} doped Zn{sub 2}SiO{sub 4} and 0.05 mol% Li{sup +} co-doped samples have been investigated. Cerium doped Zn{sub 2}SiO{sub 4} powder phosphors had broad blue emission corresponding to the 2D{sub 3/2}→2F{sub J} transition at 443nm. Stable green-yellow-red emissionmore » has been observed from Zn{sub 2}SiO{sub 4} host matrix and also we have been observed the enhanced luminescence of Li{sup +} co-doped Zn{sub 2}SiO{sub 4}:Ce{sup 3+}. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.« less

Size effect of SnO2 nanoparticles on bacteria toxicity and their membrane damage.

PubMed

Chávez-Calderón, Adriana; Paraguay-Delgado, Francisco; Orrantia-Borunda, Erasmo; Luna-Velasco, Antonia

2016-12-01

Semiconductor SnO 2 nanoparticles (NPs) are being exploited for various applications, including those in the environmental context. However, toxicity studies of SnO 2 NPs are very limited. This study evaluated the toxic effect of two sizes of spherical SnO 2 NPs (2 and 40 nm) and one size of flower-like SnO 2 NPs (800 nm) towards the environmental bacteria E. coli and B. subtilis. SnO 2 NPs were synthesized using a hydrothermal or calcination method and they were well characterized prior to toxicity assessment. To evaluate toxicity, cell viability and membrane damage were determined in cells (1 × 10 9  CFU mL -1 ) exposed to up to 1000 mg L -1 of NPs, using the plate counting method and confocal laser scanning microscopy. Spherical NPs of smaller primary size (E2) had the lowest hydrodynamic size (226 ± 96 nm) and highest negative charge (-30.3 ± 10.1 mV). Smaller spherical NPs also showed greatest effect on viability (IC 50  > 500 mg L -1 ) and membrane damage of B. subtilis, whereas E. coli was unaffected. Scanning electron microscopy confirmed the membrane damage of exposed B. subtilis and also exhibited the attachment of E2 NPs to the cell surface, as well as the elongation of cells. It was also apparent that toxicity was caused solely by NPs, as released Sn 4+ was not toxic to B. subtilis. Thus, surface charge interaction between negatively charged SnO 2 NPs and positively charged molecules on the membrane of the Gram positive B. subtilis was indicated as the key mechanism related to toxicity of NPs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Facile fabrication of a well-ordered porous Cu-doped SnO2 thin film for H2S sensing.

PubMed

Zhang, Shumin; Zhang, Pingping; Wang, Yun; Ma, Yanyun; Zhong, Jun; Sun, Xuhui

2014-09-10

Well-ordered Cu-doped and undoped SnO2 porous thin films with large specific surface areas have been fabricated on a desired substrate using a self-assembled soft template combined with simple physical cosputtering deposition. The Cu-doped SnO2 porous film gas sensor shows a significant enhancement in its sensing performance, including a high sensitivity, selectivity, and a fast response and recovery time. The sensitivity of the Cu-doped SnO2 porous sensor is 1 order of magnitude higher than that of the undoped SnO2 sensor, with average response and recovery times to 100 ppm of H2S of ∼ 10.1 and ∼ 42.4 s, respectively, at the optimal operating temperature of 180 °C. The well-defined porous sensors fabricated by the method also exhibit high reproducibility because of the accurately controlled fabrication process. The facile process can be easily extended to the fabrication of other semiconductor oxide gas sensors with easy doping and multilayer porous nanostructure for practical sensing applications.

Single step synthesis and characterization of ZnAl2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Jain, Megha; Manju, Singh, Kulwinder; Kumar, Akshay; Sharma, Jeewan; Chae, K. H.; Vij, Ankush; Thakur, Anup

2018-05-01

Zinc aluminate (ZnAl2O4) has proved to be a potential candidate in many areas such as catalysis, display panels, pigments in paints, radiation dosimetry, luminescence etc. Here, we report the solution combustion synthesis & spectroscopic studies of ZnAl2O4 nanoparticles. Urea (fuel) and metal nitrates (oxidizer) were taken in stoichiometric ratio at 1:1. The X-ray diffraction analysis of the as-prepared and annealed samples showed all reflection planes pertaining to ZnAl2O4. However, a weak intensity peak of secondary phase was also observed at 2θ value of 34.5°, which correspond to the diffraction plane (002) of ZnO. This phase was found to disappear after annealing the sample at 1000 °C for 1 hour. Fourier transform infrared spectroscopy (FTIR) also inferred the formation of ZnAl2O4. Photoluminescence measurements carried out on samples at excitation wavelength of 345 nm showed that ZnAl2O4 is an efficient luminescent material with emission in violet region of visible spectra.

Size dependent exchange bias in single-phase Zn0.3Ni0.7Fe2O4 ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Mohan, Rajendra; Ghosh, Mritunjoy Prasad; Mukherjee, Samrat

2018-07-01

We report the microstructural and magnetic characterization of single phase nanocrystalline partially inverted Zn0.3Ni0.7Fe2O4 mixed spinel ferrite. The samples were annealed at 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. X-ray diffraction results indicate phase purity of all the samples and application of Debye- Scherrer yielded a crystallite size variation from 5 nm to 33 nm for the different samples. Magnetic measurements have revealed the freezing of interfacial spins which were the cause of the large horizontal M-H loop shift causing large exchange bias with high anisotropy. The magnetic measurements show a hysteresis loop with high effective anisotropy constant due to highly magnetically disordered surface spin at 5 K.

Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

2014-11-01

This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

Structural investigations and magnetic properties of sol-gel Ni0.5Zn0.5Fe2O4 thin films for microwave heating

NASA Astrophysics Data System (ADS)

Gao, Pengzhao; Rebrov, Evgeny V.; Verhoeven, Tiny M. W. G. M.; Schouten, Jaap C.; Kleismit, Richard; Kozlowski, Gregory; Cetnar, John; Turgut, Zafer; Subramanyam, Guru

2010-02-01

Nanocrystalline Ni0.5Zn0.5Fe2O4 thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology, magnetic, and microwave absorption properties of the films calcined in the 673-1073 K range were studied with x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy, vibrating sample magnetometry, and evanescent microwave microscopy. All films were uniform without microcracks. Increasing the calcination temperature from 873 to 1073 K and time from 1 to 3 h resulted in an increase of the grain size from 12 to 27 nm. The saturation and remnant magnetization increased with increasing the grain size, while the coercivity demonstrated a maximum near a critical grain size of 21 nm due to the transition from monodomain to multidomain behavior. The complex permittivity of the Ni-Zn ferrite films was measured in the frequency range of 2-15 GHz. The heating behavior was studied in a multimode microwave cavity at 2.4 GHz. The highest microwave heating rate in the temperature range of 315-355 K was observed in the film close to the critical grain size.

Synthesis and Gas Sensing Properties of Single La-Doped SnO2 Nanobelts

PubMed Central

Wu, Yuemei; Zhang, Heng; Liu, Yingkai; Chen, Weiwu; Ma, Jiang; Li, Shuanghui; Qin, Zhaojun

2015-01-01

Single crystal SnO2 nanobelts (SnO2 NBs) and La-SnO2 nanobelts (La-SnO2 NBs) were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC) liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed. PMID:26087374

Are Ski and SnoN Involved in the Tumorigenesis of Oral Squamous Cell Carcinoma Through Smad4?

PubMed

Alaeddini, Mojgan; Etemad-Moghadam, Shahroo

2018-05-04

Transforming growth factor-β has been implicated in the tumorigenesis of oral squamous cell carcinoma (OSCC). Ski and SnoN are negative regulators of transforming growth factor-β/Smad pathway with both prooncogenic and antioncogenic functions in different cancers. The aim of this study was to assess the expression of Ski and SnoN in OSCC for the first time. Smad4 was also evaluated in these tumors. Clinical data on 61 primary OSCCs were gathered, and the specimens were subjected to immunohistochemical staining with monoclonal antibodies against SKI, SnoN, and Smad4 and scored semiquantitatively. Spearman rank, Fisher exact, and χ tests were used for statistical analysis, and P-value <0.05 was considered significant. Ski positivity and SnoN positivity were mostly cytoplasmic and found in 96.7% and 100% of the cases, respectively. Smad4 staining was low to negative in 65% of the specimens. No significant relationship was found either among the markers or between each of the proteins and the clinicopathologic data (P>0.05). According to our findings, Ski, SnoN, and Smad4 seem to play a role in OSCC oncogenesis, and we suggest that Ski and SnoN functions may take place independent of Smad4. Considering the dual and complex role of these proteins in tumorigenesis, further investigation to clarify the molecular pathways involved in their mode of action is suggested.

Novel Chemoresistive CH4 Sensor with 10 ppm Sensitivity Based on Multi-Walled Carbon Nanotubes (MWCNTs) Functionalized with SnO2nanocrystals

EPA Science Inventory

Chemoresistive sensors based on multi-walled carbon nanotubes (MWCNTs)functionalized with SnO2 nanocrystals have great potential for detecting trace gases at low concentrations (single ppm levels) at room temperature, because the SnO2 nanocrystals act as active sites for the chem...

Synthesis of new 2-amino-4H-pyran-3,5-dicarboxylate derivatives using nanocrystalline MIIZr4(PO4)6 ceramics as reusable and robust catalysts under microwave irradiation

NASA Astrophysics Data System (ADS)

Safaei-Ghomi, Javad; Javidan, Abdollah; Ziarati, Abolfazl; Shahbazi-Alavi, Hossein

2015-08-01

In the present paper, we report the successful synthesis of nanocrystalline MIIZr4(PO4)6 ceramics (M: Mn, Ni, Fe, Co). These nano-structures were characterized by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer (VSM). Size of nano-structures was in the range of 20-150 nm. Nano-MIIZr4(PO4)6 as an efficient and green catalyst has been used for the preparation of 2-amino-4H-pyran-3,5-dicarboxylate derivatives by the three-component condensation reaction of ethyl cyanoacetate, ethyl acetoacetate, and various aromatic aldehydes under microwave irradiation. Extraordinarily, the best results were obtained using MnZr4(PO4)6 nanocrystallines as an efficient catalyst. This method provides several advantages including easy work-up, excellent yields, short reaction times, using of microwave as green method, recoverability of the catalyst, and little catalyst loading.

ZrO{sub 2}-ZnO composite thin films for humidity sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velumani, M., E-mail: velumanimohan@gmail.com; Sivacoumar, R.; Alex, Z. C.

2016-05-23

ZrO{sub 2}-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO{sub 2} phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

The Assessment for Sensitivity of a NO2 Gas Sensor with ZnGa2O4/ZnO Core-Shell Nanowires—a Novel Approach

PubMed Central

Chen, I-Cherng; Lin, Shiu-Shiung; Lin, Tsao-Jen; Hsu, Cheng-Liang; Hsueh, Ting Jen; Shieh, Tien-Yu

2010-01-01

The application of novel core-shell nanowires composed of ZnGa2O4/ZnO to improve the sensitivity of NO2 gas sensors is demonstrated in this study. The growth of ZnGa2O4/ZnO core-shell nanowires is performed by reactive evaporation on patterned ZnO:Ga/SiO2/Si templates at 600 °C. This is to form the homogeneous structure of the sensors investigated in this report to assess their sensitivity in terms of NO2 detection. These novel NO2 gas sensors were evaluated at working temperatures of 25 °C and at 250 °C, respectively. The result reveals the ZnGa2O4/ZnO core-shell nanowires present a good linear relationship (R2 > 0.99) between sensitivity and NO2 concentration at both working temperatures. These core-shell nanowire sensors also possess the highest response (<90 s) and recovery (<120 s) values with greater repeatability seen for NO2 sensors at room temperature, unlike traditional sensors that only work effectively at much higher temperatures. The data in this study indicates the newly-developed ZnGa2O4/ZnO core-shell nanowire based sensors are highly promising for industrial applications. PMID:22319286

Transparent nanocrystalline ZnO and ZnO:Al coatings obtained through ZnS sols

NASA Astrophysics Data System (ADS)

Kolobkova, E. V.; Evstropiev, S. K.; Nikonorov, N. V.; Vasilyev, V. N.; Evstropyev, K. S.

2017-11-01

Thin and uniform ZnO and ZnO:Al coatings were prepared on glass surfaces by using film-forming colloidal solutions containing small ZnS nanoparticles and polyvinylpyrrolidone as a polymer stabilizer. Film-forming ZnS sols were synthesized in the mixed water-propanol-2 solutions by chemical reaction between zinc nitrate and sodium sulfide. The addition of modifying component such as Al(NO3)3 into the film-forming solutions allows one to obtain thin and uniform ZnO:Al coatings. An increase in the sodium sulfide content in film-forming solutions leads to the growth of light absorption in the UV. The evolution of a coating material at all technological stages from the ZnS sols up to the transparent ZnO and ZnO:Al2O3 coatings (the latter kind being denoted further, in accord with a common practice, by ZnO:Al) was studied using the optical spectroscopy, XRD analysis, DSC-TGA, and SEM methods. The chemical processes of decomposing salts and the polymer occur by heating the intermediate composite ZnS/polyvinylpyrrolidone coatings in the 280-500 °C temperature range. Experimental data show that the ZnO and ZnO:Al coatings prepared consist of the slightly elongated oxide nanoparticles. These coatings fully cover the glass surface and demonstrate a high transparency in the UV and visible.

Electrospinning Hetero-Nanofibers In2O3/SnO2 of Homotype Heterojunction with High Gas Sensing Activity

PubMed Central

Du, Haiying; Yao, PengJun; Sun, Yanhui; Wang, Jing; Wang, Huisheng; Yu, Naisen

2017-01-01

In2O3/SnO2 composite hetero-nanofibers were synthesized by an electrospinning technique for detecting indoor volatile organic gases. The physical and chemical properties of In2O3/SnO2 hetero-nanofibers were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), Energy Dispersive X-Ray Spectroscopy (EDX), specific surface Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS). Gas sensing properties of In2O3/SnO2 composite hetero-nanofibers were measured with six kinds of indoor volatile organic gases in concentration range of 0.5~50 ppm at the operating temperature of 275 °C. The In2O3/SnO2 composite hetero-nanofibers sensor exhibited good formaldehyde sensing properties, which would be attributed to the formation of n-n homotype heterojunction in the In2O3/SnO2 composite hetero-nanofibers. Finally, the sensing mechanism of the In2O3/SnO2 composite hetero-nanofibers was analyzed based on the energy-band principle. PMID:28792433

Effect of vacuum annealing and substrate temperature on structural and optical properties of ZnIn2Se4 thin films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Salem, G. F.; Ali, H. A. M.; Ismail, M. I.

2013-09-01

Zinc indium selenide (ZnIn2Se4) thin films were prepared by the thermal evaporation technique with high deposition rate. The effect of thermal annealing in vacuum on the crystallinity of the as-deposited films was studied at different temperatures (523, 573 and 623 K). The effect of substrate temperature (623 K) for different thickness values (173, 250, 335 and 346 nm) on the optical parameters of ZnIn2Se4 was also studied. The structural studies showed nanocrystalline nature of the room temperature (300 K) deposited films with crystallite size of about a few nanometers. The crystallite size increased up to 31 nm with increasing the annealing temperature in vacuum. From the reflection and transmission data, the refractive index n and the extinction coefficient k were estimated for ZnIn2Se4 thin films and they were found to be independent of film thickness. Analysis of the absorption coefficient data of the as-deposited films revealed the existence of allowed direct and indirect transitions with optical energy gaps of 2.21 eV and 1.71 eV, respectively. These values decreased with increasing annealing temperature. At substrate temperature of 623 K, the direct band gap increased to 2.41 eV whereas the value of indirect band gap remained nearly unchanged. The dispersion analysis showed that the values of the oscillator energy Eo, dispersion energy Ed, dielectric constant at infinite frequency ε∞, and lattice dielectric constant εL were changed appreciably under the effect of annealing and substrate temperature. The covalent nature of structure was studied as a function of the annealing and substrate temperature using an empirical relation for the dispersion energy Ed. Generalized Miller's rule and linear refractive index were used to estimate the nonlinear susceptibility and nonlinear refractive index of the thin films.

Synthesis and characterization of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO nanocomposites from waste batteries for photocatalytic, electrochemical and thermal studies

NASA Astrophysics Data System (ADS)

Mylarappa, M.; Venkata Lakshmi, V.; Vishnu Mahesh, K. R.; Nagaswarupa, H. P.; Raghavendra, N.

2017-11-01

In the present paper, Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO composites recovered from waste batteries using acid dissolution and ferrite processing were studied. The recovered Mn-ZnFe2O4 nanocomposites were decorated onto rGO using the facile hydrothermal method. The recovered material was characterized using x-ray powder diffraction to study the particle size and crystallinity. The morphology of the composites was analyzed using scanning electron microscopy, and elements present in the materials were studied using energy dispersive x-ray analysis. The functional groups attached were observed using a Fourier transform infrared spectrometer. Furthermore, the recovered composites were evaluated in thermal studies using thermal gravimetric analysis, differential scanning calorimetry and dynamic thermal analysis. The material was used as a photocatalyst for the removal of acid orange 88 dye, and as an electrocatalyst. The decreased band gap energy for the Mn-ZnFe2O4/rGO composite was displayed in better photocatalytic activity for a given reaction. The electrochemical properties of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with a paste-type electrode. The CV indicated the reversibility of the electrode reaction, and the EIS revealed that a decrease in the charge transfer resistance increases the double layer capacitance of the rGO/Mn-ZnFe2O4 electrode.

SnO2/CNT nanocomposite supercapacitors fabricated using scanning atmospheric-pressure plasma jets

NASA Astrophysics Data System (ADS)

Xu, Chang-Han; Chiu, Yi-Fan; Yeh, Po-Wei; Chen, Jian-Zhang

2016-08-01

SnO2/CNT electrodes for supercapacitors are fabricated by first screen-printing pastes containing SnO2 nanoparticles and CNTs on carbon cloth, following which nitrogen atmospheric pressure plasma jet (APPJ) sintering is performed at various APPJ scan rates. The APPJ scan rates change the time intervals for which the reactive plasma species and the heat of the nitrogen APPJs influence the designated sintering spot on the carbon cloth, resulting in APPJ-sintered SnO2/CNT nanocomposites with different properties. The water contact angle decreases with the APPJ scan rate. The improved wettability can facilitate the penetration of the electrolyte into the nanopores of the SnO2/CNT nanocomposites, thereby improving the charge storage and specific capacitance of the supercapacitors. Among the three tested APPJ scan rates, 1.5, 3, and 6 mm s-1, the SnO2/CNT supercapacitor sintered by APPJ under the lowest APPJ scan rate of 1.5 mm s-1 shows the best specific capacitance of ˜90 F g-1 as evaluated by cyclic voltammetry under a potential scan rate of 2 mV s-1. A high APPJ scan rate may result in low degree of materials activation and sintering, leading to poorer performance of SnO2/CNT supercapacitors. The results suggest the feasibility of an APPJ roll-to-roll process for the fabrication of SnO2/CNT nanocomposite supercapacitors.

Heterojunction Fe2O3-SnO2 Nanostructured Photoanode for Efficient Photoelectrochemical Water Splitting

NASA Astrophysics Data System (ADS)

Han, Hyun Soo; Shin, Sun; Noh, Jun Hong; Cho, In Sun; Hong, Kug Sun

2014-04-01

Hierarchically organized nanostructures were fabricated by growing SnO2 nanoparticles on a fluorine-doped tin oxide/glass substrate via a laser ablation method. Cauliflower-like clusters consisting of agglomerated nanoparticles were deposited and aligned with respect to the substrate with a large internal surface area and open channels of pores. The morphological changes of SnO2 nanostructured films were investigated as a function of the oxygen working pressure in the range of 100-500 mTorr. A nanostructured scaffold prepared at an oxygen working pressure of 100 mTorr exhibited the best photoelectrochemical (PEC) performance. A Ti:Fe2O3-SnO2 nanostructured photoanode showed the photocurrent that was 34% larger than that of a Ti:Fe2O3 flat photoanode when the amount of Ti:Fe2O3 sensitizer was identical for the two photoanodes. The larger surface area and longer electron lifetime of the Ti:Fe2O3-SnO2 nanostructured photoanode explains its improved PEC performance.

Synthesis, characterization, and magnetic properties of ZnO-ZnFe2O4 nanoparticles with high photocatalytic activity

NASA Astrophysics Data System (ADS)

Falak, P.; Hassanzadeh-Tabrizi, S. A.; Saffar-Teluri, A.

2017-11-01

In the present research, a magnetic ZnO-ZnFe2O4 binary nanocomposite was synthesized by a one-step microemulsion method. The characteristics of the synthesized powders were characterized using various analytical instruments including X-ray diffraction, scanning electron microscope, transmission electron microscope, thermogravimetric and differential thermal analysis, vibrating sample magnetometer, and ultraviolet-visible spectroscopy. The results of transmission electron microscope proved that the synthesized nanoparticles have irregular morphologies and the average particle size is about 20 nm. The photocatalytic investigation of ZnO-ZnFe2O4 nanoparticles was carried out using methylene blue solution under UV light. The synthesized nanoparticles showed enhanced photocatalytic performance in comparison with the ZnO nanoparticles more than 40%. The magnetization saturation value of ZnO-ZnFe2O4 nanoparticles was about 5.8 emu/g, which was high enough to be magnetically removed by applying a magnetic field. The results showed that the magnetization and coercivity of the samples reduced by increasing calcination temperature.

On the physics of dispersive electron transport characteristics in SnO2 nanoparticle-based dye sensitized solar cells.

PubMed

Ashok, Aditya; Vijayaraghavan, S N; Unni, Gautam E; Nair, Shantikumar V; Shanmugam, Mariyappan

2018-04-27

The present study elucidates dispersive electron transport mediated by surface states in tin oxide (SnO 2 ) nanoparticle-based dye sensitized solar cells (DSSCs). Transmission electron microscopic studies on SnO 2 show a distribution of ∼10 nm particles exhibiting (111) crystal planes with inter-planar spacing of 0.28 nm. The dispersive transport, experienced by photo-generated charge carriers in the bulk of SnO 2 , is observed to be imposed by trapping and de-trapping processes via SnO 2 surface states present close to the band edge. The DSSC exhibits 50% difference in performance observed between the forward (4%) and reverse (6%) scans due to the dispersive transport characteristics of the charge carriers in the bulk of the SnO 2 . The photo-generated charge carriers are captured and released by the SnO 2 surface states that are close to the conduction band-edge resulting in a very significant variation; this is confirmed by the hysteresis observed in the forward and reverse scan current-voltage measurements under AM1.5 illumination. The hysteresis behavior assures that the charge carriers are accumulated in the bulk of electron acceptor due to the trapping, and released by de-trapping mediated by surface states observed during the forward and reverse scan measurements.

On the physics of dispersive electron transport characteristics in SnO2 nanoparticle-based dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Ashok, Aditya; Vijayaraghavan, S. N.; Unni, Gautam E.; Nair, Shantikumar V.; Shanmugam, Mariyappan

2018-04-01

The present study elucidates dispersive electron transport mediated by surface states in tin oxide (SnO2) nanoparticle-based dye sensitized solar cells (DSSCs). Transmission electron microscopic studies on SnO2 show a distribution of ˜10 nm particles exhibiting (111) crystal planes with inter-planar spacing of 0.28 nm. The dispersive transport, experienced by photo-generated charge carriers in the bulk of SnO2, is observed to be imposed by trapping and de-trapping processes via SnO2 surface states present close to the band edge. The DSSC exhibits 50% difference in performance observed between the forward (4%) and reverse (6%) scans due to the dispersive transport characteristics of the charge carriers in the bulk of the SnO2. The photo-generated charge carriers are captured and released by the SnO2 surface states that are close to the conduction band-edge resulting in a very significant variation; this is confirmed by the hysteresis observed in the forward and reverse scan current-voltage measurements under AM1.5 illumination. The hysteresis behavior assures that the charge carriers are accumulated in the bulk of electron acceptor due to the trapping, and released by de-trapping mediated by surface states observed during the forward and reverse scan measurements.

SnO2 quantum dots with rapid butane detection at lower ppm-level

NASA Astrophysics Data System (ADS)

Cai, Pan; Dong, Chengjun; Jiang, Ming; Shen, Yuanyuan; Tao, You; Wang, Yude

2018-04-01

SnO2 quantum dots (QDs) were successfully synthesized by a facile approach employing benzyl alcohol and ammonium hydroxide at lower temperature of 130 °C. It is revealed that the SnO2 QDs is about 3 nm in size to form clusters. The gas sensor based on SnO2 QDs shows a high potential for detecting low-ppm-level butane at 400 °C, exhibiting a high sensitivity, short response and rapid recovery time, and effective selectivity. The sensing mechanism is understood in terms of adsorbed oxygen species. Significantly, the excellent sensing performance is attributed to the smaller size of SnO2 and larger surface area (204.85 m2/g).

Probing the Failure Mechanism of SnO2 Nanowires for Sodium-ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Meng; Kushima, Akihiro; Shao, Yuyan

2013-09-30

Non-lithium metals such as sodium have attracted wide attention as a potential charge carrying ion for rechargeable batteries, performing the same role as lithium in lithium- ion batteries. As sodium and lithium have the same +1 charge, it is assumed that what has been learnt about the operation of lithium ion batteries can be transferred directly to sodium batteries. Using in-situ TEM, in combination with DFT calculations, we probed the structural and chemical evolution of SnO2 nanowire anodes in Na-ion batteries and compared them quantitatively with results from Li-ion batteries [Science 330 (2010) 1515]. Upon Na insertion into SnO2, amore » displacement reaction occurs, leading to the formation of amorphous NaxSn nanoparticles covered by crystalline Na2O shell. With further Na insertion, the NaxSn core crystallized into Na15Sn4 (x=3.75). Upon extraction of Na (desodiation), the NaxSn core transforms to Sn nanoparticles. Associated with a volume shrinkage, nanopores appear and metallic Sn particles are confined in hollow shells of Na2O, mimicking a peapod structure. These pores greatly increase electrical impedance, therefore naturally accounting for the poor cyclability of SnO2. DFT calculations indicate that Na+ diffuses 30 times slower than Li+ in SnO2, in agreement with in-situ TEM measurement. Insertion of Na can chemo-mechanically soften the reaction product to greater extent than in lithiation. Therefore, in contrast to the lithiation of SnO2, no dislocation plasticity was seen ahead of the sodiation front. This direct comparison of the results from Na and Li highlights the critical role of ionic size and electronic structure of different ionic species on the charge/discharge rate and failure mechanisms in these batteries.« less

Strain effect in epitaxial VO2 thin films grown on sapphire substrates using SnO2 buffer layers

NASA Astrophysics Data System (ADS)

Kim, Heungsoo; Bingham, Nicholas S.; Charipar, Nicholas A.; Piqué, Alberto

2017-10-01

Epitaxial VO2/SnO2 thin film heterostructures were deposited on m-cut sapphire substrates via pulsed laser deposition. By adjusting SnO2 (150 nm) growth conditions, we are able to control the interfacial strain between the VO2 film and SnO2 buffer layer such that the semiconductor-to-metal transition temperature (TC) of VO2 films can be tuned without diminishing the magnitude of the transition. It is shown that in-plane tensile strain and out-of-plane compressive strain of the VO2 film leads to a decrease of Tc. Interestingly, VO2 films on SnO2 buffer layers exhibit a structural phase transition from tetragonal-like VO2 to tetragonal-VO2 during the semiconductor-to-metal transition. These results suggest that the strain generated by SnO2 buffer provides an effective way for tuning the TC of VO2 films.

Data of chemical analysis and electrical properties of SnO2-TiO2 composite nanofibers.

PubMed

Bakr, Zinab H; Wali, Qamar; Ismail, Jamil; Elumalai, Naveen Kumar; Uddin, Ashraf; Jose, Rajan

2018-06-01

In this data article, we provide energy dispersive X-ray spectroscopy (EDX) spectra of the electrospun composite (SnO 2 -TiO 2 ) nanowires with the elemental values measured in atomic and weight%. The linear sweep voltammetry data of composite and its component nanofibers are provided. The data collected in this article is directly related to our research article "Synergistic combination of electronic and electrical properties of SnO 2 and TiO 2 in a single SnO 2 -TiO 2 composite nanowire for dye-sensitized solar cells" [1].

Ultrafast Recombination Dynamics in Dye-Sensitized SnO2/TiO2 Core/Shell Films.

PubMed

Gish, Melissa K; Lapides, Alexander M; Brennaman, M Kyle; Templeton, Joseph L; Meyer, Thomas J; Papanikolas, John M

2016-12-15

Interfacial dynamics are investigated in SnO 2 /TiO 2 core/shell films derivatized with a Ru(II)-polypyridyl chromophore ([Ru II (bpy) 2 (4,4'-(PO 3 H 2 ) 2 bpy)] 2+ , RuP) using transient absorption methods. Electron injection from the chromophore into the TiO 2 shell occurs within a few picoseconds after photoexcitation. Loss of the oxidized dye through recombination occurs across time scales spanning 10 orders of magnitude. The majority (60%) of charge recombination events occur shortly after injection (τ = 220 ps), while a small fraction (≤20%) of the oxidized chromophores persists for milliseconds. The lifetime of long-lived charge-separated states (CSS) depends exponentially on shell thickness, suggesting that the injected electrons reside in the SnO 2 core and must tunnel through the TiO 2 shell to recombine with oxidized dyes. While the core/shell architecture extends the lifetime in a small fraction of the CSS, making water oxidation possible, the subnanosecond recombination process has profound implications for the overall efficiencies of dye-sensitized photoelectrosynthesis cells (DSPECs).

Magnetic properties of Mn0.1Mg0.2TM0.7Fe2O4 (TM = Zn, Co, or Ni) prepared by hydrothermal processes: The effects of crystal size and chemical composition

NASA Astrophysics Data System (ADS)

Nhlapo, T. A.; Msomi, J. Z.; Moyo, T.

2018-02-01

Nano-crystalline Zn-, Co-, and Ni-substituted Mn-Mg ferrites were prepared by hydrothermal process and annealed at 1100 °C. Annealing conditions are critical on the crystalline phase. TEM and XRD data reveal particle sizes between 8 nm and 15 nm for the as-prepared fine powders, which increase to about 73 nm after sintering at 1100 °C. Mӧssbauer spectra show well resolved magnetic splitting in bulk samples. The as-prepared fine powders show weak hyperfine splitting and broad central doublets associated with fine particles. Magnetization data reveal a high coercive field at about 300 K of about 945 Oe in the Co-based nanosized oxide, which reduces to about 360 Oe after thermal annealing at 1100 °C. The magnetization curves of Zn- and Ni-based samples show much lower coercive fields indicative of superparamagnetic nanoparticles. The crystallite size and chemical composition have significant effects on the properties of Mn0.1Mg0.2(Zn,Co,Ni)0.7Fe2O4 investigated.

Photocatalytic degradation of diclofenac using TiO2-SnO2 mixed oxide catalysts.

PubMed

Mugunthan, E; Saidutta, M B; Jagadeeshbabu, P E

2017-12-26

The complex nature of diclofenac limits its biological degradation, posing a serious threat to aquatic organisms. Our present work aims to eliminate diclofenac from wastewater through photocatalytic degradation using TiO 2 -SnO 2 mixed-oxide catalysts under various operating conditions such as catalyst loading, initial diclofenac concentration and initial pH. Different molar ratios of Ti-Sn (1:1, 5:1, 10:1, 20:1 and 30:1) were prepared by the hydrothermal method and were characterized. The results indicated that addition of Sn in small quantity enhances the catalytic activity of TiO 2 . Energy Band gap of the TiO 2 -SnO 2 catalysts was found to increase with an increase in Tin content. TiO 2 -SnO 2 catalyst with a molar ratio of 20:1 was found to be the most effective when compared to other catalysts. The results suggested that initial drug concentration of 20 mg/L, catalyst loading of 0.8 g/L and pH 5 were the optimum operating conditions for complete degradation of diclofenac. Also, the TiO 2 -SnO 2 catalyst was effective in complete mineralization of diclofenac with a maximum total organic carbon removal of 90% achieved under ultraviolet irradiation. The repeatability and stability results showed that the TiO 2 -SnO 2 catalyst exhibited an excellent repeatability and better stability over the repeated reaction cycles. The photocatalytic degradation of diclofenac resulted in several photoproducts, which were identified through LC-MS.

Gas-sensing enhancement methods for hydrothermal synthesized SnO2-based sensors

NASA Astrophysics Data System (ADS)

Zhao, Yalei; Zhang, Wenlong; Yang, Bin; Liu, Jingquan; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng

2017-11-01

Gas sensing for hydrothermal synthesized SnO2-based gas sensors can be enhanced in three ways: structural improvement, composition optimization, and processing improvement. There have been zero-dimensional, one-dimensional, and three-dimensional structures reported in the literature. Controllable synthesis of different structures has been deployed to increase specific surface area. Change of composition would intensively tailor the SnO2 structure, which affected the gas-sensing performance. Furthermore, doping and compounding methods have been adopted to promote gas-sensing performance by adjusting surface conditions of SnO2 crystals and constructing heterojunctions. As for processing area, it is very important to find the optimal reaction time and temperature. In this paper, a gas-solid reaction rate constant was proposed to evaluate gas-sensing properties and find an excellent hydrothermal synthesized SnO2-based gas sensor.

Metal-to-insulator transition induced by UV illumination in a single SnO2 nanobelt

NASA Astrophysics Data System (ADS)

Viana, E. R.; Ribeiro, G. M.; de Oliveira, A. G.; González, J. C.

2017-11-01

An individual tin oxide (SnO2) nanobelt was connected in a back-gate field-effect transistor configuration and the conductivity of the nanobelt was measured at different temperatures from 400 K to 4 K, in darkness and under UV illumination. In darkness, the SnO2 nanobelts showed semiconductor behavior for the whole temperature range measured. However, when subjected to UV illumination the photoinduced carriers were high enough to lead to a metal-to-insulator transition (MIT), near room temperature, at T MIT = 240 K. By measuring the current versus gate voltage curves, and considering the electrostatic properties of a non-ideal conductor, for the SnO2 nanobelt on top of a gate-oxide substrate, we estimated the capacitance per unit length, the mobility and the density of carriers. In darkness, the density was estimated to be 5-10 × 1018 cm-3, in agreement with our previously reported result (Phys. Status Solid. RRL 6, 262-4 (2012)). However, under UV illumination the density of carriers was estimated to be 0.2-3.8 × 1019 cm-3 near T MIT, which exceeded the critical Mott density estimated to be 2.8 × 1019 cm-3 above 240 K. These results showed that the electrical properties of the SnO2 nanobelts can be drastically modified and easily tuned from semiconducting to metallic states as a function of temperature and light.

Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukoje, Ivana D., E-mail: ivanav@vinca.rs; Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com; Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com

Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical andmore » morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.« less

Double Z-scheme ZnO/ZnS/g-C3N4 ternary structure for efficient photocatalytic H2 production

NASA Astrophysics Data System (ADS)

Dong, Zhifang; Wu, Yan; Thirugnanam, Natarajan; Li, Gonglin

2018-02-01

In the present work, a novel ZnO/ZnS/g-C3N4 ternary nanocomposite with double Z-scheme heterojunction has been designed via a two-step facile chemical conversion route. The spherical ZnS nanoparticles were uniformly loaded onto ZnO nanoflowers surface. And then the ZnO/ZnS nanocomposite was further hybridized with g-C3N4 nanosheets. Ternary ZnO/ZnS/g-C3N4 nanocomposite displays the largest specific surface area (about 76.2 m2/g), which provides plentiful activated sites for photocatalytic reaction. Furthermore, the ternary material exhibits the highest methylene blue photodegradation rate of about 0.0218 min-1 and the optimum photocatalytic H2 production (1205 μmol/g) over water splitting at 4 h under solar light irradiation. Moreover, it showed the highest photocurrent effect and the minimum charge-transfer resistance. These results implied that the higher photoactivity of ZnO/ZnS/g-C3N4 nanocomposite could be attributed to the multi-steps charge transfer and effective electron-hole separation in the double Z-scheme system.

Preparation of Ru-doped SnO2-supported Pt catalysts and their electrocatalytic properties for methanol oxidation.

PubMed

Pang, H L; Zhang, X H; Zhong, X X; Liu, B; Wei, X G; Kuang, Y F; Chen, J H

2008-03-01

Ru-doped SnO2 nanoparticles were prepared by chemical precipitation and calcinations at 823 K. Due to high stability in diluted acidic solution, Ru-doped SnO2 nanoparticles were selected as the catalyst support and second catalyst for methanol electrooxidation. The micrograph, elemental composition, and structure of the Ru-doped SnO2 nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. The electrocatalytic properties of the Ru-doped SnO2-supported Pt catalyst (Pt/Ru-doped SnO2) for methanol oxidation have been investigated by cyclic voltammetry. Under the same loading mass of Pt, the Pt/Ru-doped SnO2 catalyst shows better electrocatalytic performance than the Pt/SnO2 catalyst and the best atomic ratio of Ru to Sn in Ru-doped SnO2 is 1/75. Additionally, the Pt/Ru-doped SnO2 catalyst possesses good long-term cycle stability.

First-principles study of defect formation in a photovoltaic semiconductor Cu2ZnGeSe4

NASA Astrophysics Data System (ADS)

Nishihara, Hironori; Maeda, Tsuyoshi; Wada, Takahiro

2018-02-01

The formation energies of neutral Cu, Zn, Ge, and Se vacancies in kesterite-type Cu2ZnGeSe4 were evaluated by first-principles pseudopotential calculations using plane-wave basis functions. The calculations were performed at typical points in Cu-(Zn1/2Ge1/2)-Se and Cu3Se2-ZnSe-GeSe2 pseudoternary phase diagrams for Cu2ZnGeSe4. The results were compared with those for Cu2ZnSnSe4, Cu2ZnGeS4, and Cu2ZnSnS4 calculated using the same version of the CASTEP program code. The results indicate that Cu vacancies are easily formed in Cu2ZnGeSe4 under the Cu-poor condition as in the above compounds and CuInSe2, suggesting that Cu2ZnGeSe4 is also a preferable p-type absorber material for thin-film solar cells. The formation energies of possible antisite defects, such as CuZn and CuGe, and of possible complex defects, such as CuZn+ZnCu, were also calculated and compared within the above materials. The antisite defect of CuZn, which has the smallest formation energy within the possible defects, is concluded to be the most hardly formed in Cu2ZnGeSe4 among the compounds.

Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

NASA Astrophysics Data System (ADS)

Pedersen, Joachim D.; Esposito, Heather J.; Teh, Kwok Siong

2011-10-01

We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.

Synthesis of nanodimensional orthorhombic SnO2 thin films

NASA Astrophysics Data System (ADS)

Kondkar, V.; Rukade, D.; Kanjilal, D.; Bhattacharyya, V.

2018-04-01

Amorphous thin films of SnO2 are irradiated by swift heavy ions at two different fluences. Unirradiated as well as irradiated films are characterized by glancing angle X-ray diffraction (GAXRD), UV-Vis spectroscopy and atomic force microscopy (AFM). GAXRD study reveals formation of orthorhombic nanophases of SnO2. Nanophase formation is also confirmed by the quantum size effect manifested by blue shift in terms of increase in band gap energy. The size and shape of the irradiation induced surface structures depend on ion fluence.

Syntheses, structures and properties of homo- and heterobimetallic complexes of the type [Zn(tren)NCS] 2[M(NCS) 4] [tren = tris(2-aminoethyl)amine; M = Zn, Cu

NASA Astrophysics Data System (ADS)

Chattopadhyay, Soumi; Bhar, Kishalay; Das, Sumitra; Chantrapromma, Suchada; Fun, Hoong-Kun; Ghosh, Barindra Kumar

2010-04-01

A 2:2:1:6 molar ratio of Zn(ClO 4) 2·6H 2O, tris(2-aminoethyl)amine (tren), Zn(ClO 4) 2·6H 2O/Cu(ClO 4) 2·6H 2O and NH 4NCS in methanol-water solution mixtures affords homo-/heterobimetallic compounds of the type [Zn(tren)NCS] 2[M(NCS) 4] (M = Zn, 1; M = Cu, 2) which have been characterized using microanalytical, spectroscopic, magnetic and other physicochemical results. The structures of the compounds are determined by X-ray diffraction measurements. Structural analyses reveal that 1 and 2 are isomorphous and consist of two discrete [Zn(tren)NCS] + cations and a [M(NCS) 4] 2- (M = Zn/Cu) anion. Zinc(II) centers in the [Zn(tren)NCS] + units adopt distorted trigonal bipyramidal geometry with ZnN 5 chromophores coordinated through four N atoms of tren and one N atom of terminal thiocyanate. Each metal(II) center in [M(NCS) 4] 2- has a distorted tetrahedral coordination environment with an MN 4 chromophore ligated by four N atoms of the terminal thiocyanates. In solid state, doubly N-H…S hydrogen bonded 1D chains of [Zn(tren)NCS] + cations are interconnected by tetrahedral [Zn(NCS) 4] 2-/[Cu(NCS) 4] 2- anions through cooperative N-H…S and N-H…N (in 1) and N-H…S and C-H…S (in 2) hydrogen bonds resulting in 3D network structures. Establishment of such networks seems to be aiding the crystallization.

Zn2GeO4 nanowires as efficient electron injection material for electroluminescent devices.

PubMed

Wang, Jiangxin; Yan, Chaoyi; Magdassi, Shlomo; Lee, Pooi See

2013-08-14

Pure phase Zn2GeO4 nanowires (NWs) were grown by the chemical vapor transport method on p-GaN: Mg/Al2O3 substrate. The as-grown Zn2GeO4 NWs exhibited n-type characteristic due to native defects and formed a p-n heterojunction with the p-GaN substrate. The unique energy level of Zn2GeO4 NWs promotes electron injection into GaN active region while suppressing hole injection into Zn2GeO4 NWs. The device exhibited an emission centered at 426 nm and a low turn-on voltage around 4 V. Zn2GeO4 NWs are first reported in this paper as promising electron transport and injection material for electroluminescent devices.

Synthesis and property of spinel porous ZnMn2O4 microspheres

NASA Astrophysics Data System (ADS)

Guo, N.; Wei, X. Q.; Deng, X. L.; Xu, X. J.

2015-11-01

Mesoporous ternary zinc manganese oxides on the Ti sheet substrate are prepared by easy and fast hydrothermal method for the first time. The obtained ZnMn2O4 materials with homogenously distributed pores have been characterized by XRD, SEM and Raman spectra, which show the good crystal phase and particles for improving supercapacitive performance. XRD and SEM images show that the as-prepared samples have good crystallinity, and ZnMn2O4 microsphere has an average diameter of 10 μm. In addition, ZnMn2O4 are also characterized in 2 M KOH solution using three-electrode system. In the work, we study that different substrates (Ti, carbon and nickel foam) have an important effect on the electrochemical performance of the samples. The research of cyclic voltammogram (CV) indicates that the obtained specific capacitance (155 F g-1) values on nickel foam substrate for the ZnMn2O4 microspheres are higher than the values reported for some inexpensive oxides. However, the specific capacitance of all ZnMn2O4 samples has almost no change at two different scan rates which shows good long-term cycling stability. The electrochemical impedance spectroscopy with a small resistance reveals that the as-synthesized samples have good frequency response characteristics. These results indicate that the unique ZnMn2O4 electrode would be a promising electrode for high-performance supercapacitor applications.

Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

PubMed

Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

2017-09-20

Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo 2 O 4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo 2 O 4 /C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo 2 O 4 /C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo 2 O 4 /C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo 2 O 4 /C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo 2 O 4 /C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo 2 O 4 /C nanocages.

[Ski and SnoN: antagonistic proteins of TGFbeta signaling].

PubMed

Vignais, M L

2000-02-01

Ski and SnoN are two proto-oncogenes that, at high cellular concentrations, are associated with tumors. Up to now, apart the fact that SnoN and Ski were known to bind to DNA indirectly, very little was known about the mechanism which enables these factors to induce tumorigenesis. We know now that SnoN and Ski interact with the SMAD proteins which are mediators of TGFbeta signaling. These SMADs enable recruitment to target gene promoters of SnoN and Ski as well as the histone deacetylase activity which is associated with them. Whereas physiologic concentrations of SnoN and Ski allow a feedback regulation of TGFbeta signaling, deregulation of SnoN or Ski expression leads to total inhibition of TGFbeta signaling and of the tumor suppressors Smad2 and Smad4, which can explain the role of SnoN and Ski as oncogenes.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

A novel snowflake-like SnO2 hierarchical architecture with superior gas sensing properties

NASA Astrophysics Data System (ADS)

Li, Yanqiong

2018-02-01

Snowflake-like SnO2 hierarchical architecture has been synthesized via a facile hydrothermal method and followed by calcination. The SnO2 hierarchical structures are assembled with thin nanoflakes blocks, which look like snowflake shape. A possible mechanism for the formation of the SnO2 hierarchical structures is speculated. Moreover, gas sensing tests show that the sensor based on snowflake-like SnO2 architectures exhibited excellent gas sensing properties. The enhancement may be attributed to its unique structures, in which the porous feature on the snowflake surface could further increase the active surface area of the materials and provide facile pathways for the target gas.

Fabrication of textured SnO2 transparent conductive films using self-assembled Sn nanospheres

NASA Astrophysics Data System (ADS)

Fukumoto, Michitaka; Nakao, Shoichiro; Hirose, Yasushi; Hasegawa, Tetsuya

2018-06-01

We present a novel method to fabricate textured surfaces on transparent conductive SnO2 films by processing substrates through a bottom-up technique with potential for industrially scalable production. The substrate processing consists of three steps: deposition of precursor Sn films on glass substrates, formation of a self-assembled Sn nanosphere layer with reductive annealing, and conversion of Sn to SnO2 by oxidative annealing. Ta-doped SnO2 films conformally deposited on the self-assembled nanospherical SnO2 templates exhibited attractive optical and electrical properties, namely, enhanced haze values and low sheet resistances, for applications as transparent electrodes in photovoltaics.

SnO2@C@VO2 Composite Hollow Nanospheres as an Anode Material for Lithium-Ion Batteries.

PubMed

Guo, Wenbin; Wang, Yong; Li, Qingyuan; Wang, Dongxia; Zhang, Fanchao; Yang, Yiqing; Yu, Yang

2018-05-02

Porous SnO 2 @C@VO 2 composite hollow nanospheres were ingeniously constructed through the combination of layer-by-layer deposition and redox reaction. Moreover, to optimize the electrochemical properties, SnO 2 @C@VO 2 composite hollow nanospheres with different contents of the external VO 2 were also studied. On the one hand, the elastic and conductive carbon as interlayer in the SnO 2 @C@VO 2 composite can not only buffer the huge volume variation during repetitive cycling but also effectively improve electronic conductivity and enhance the utilizing rate of SnO 2 and VO 2 with high theoretical capacity. On the other hand, hollow nanostructures of the composite can be consolidated by the multilayered nanocomponents, resulting in outstanding cyclic stability. In virtue of the above synergetic contribution from individual components, SnO 2 @C@VO 2 composite hollow nanospheres exhibit a large initial discharge capacity (1305.6 mAhg -1 ) and outstanding cyclic stability (765.1 mAhg -1 after 100 cycles). This design of composite hollow nanospheres may be extended to the synthesis of other nanomaterials for electrochemical energy storage.

Cation-Deficient Spinel ZnMn2O4 Cathode in Zn(CF3SO3)2 Electrolyte for Rechargeable Aqueous Zn-Ion Battery.

PubMed

Zhang, Ning; Cheng, Fangyi; Liu, Yongchang; Zhao, Qing; Lei, Kaixiang; Chen, Chengcheng; Liu, Xiaosong; Chen, Jun

2016-10-05

Rechargeable aqueous Zn-ion batteries are attractive cheap, safe and green energy storage technologies but are bottlenecked by limitation in high-capacity cathode and compatible electrolyte to achieve satisfactory cyclability. Here we report the application of nonstoichiometric ZnMn 2 O 4 /carbon composite as a new Zn-insertion cathode material in aqueous Zn(CF 3 SO 3 ) 2 electrolyte. In 3 M Zn(CF 3 SO 3 ) 2 solution that enables ∼100% Zn plating/stripping efficiency with long-term stability and suppresses Mn dissolution, the spinel/carbon hybrid exhibits a reversible capacity of 150 mAh g -1 and a capacity retention of 94% over 500 cycles at a high rate of 500 mA g -1 . The remarkable electrode performance results from the facile charge transfer and Zn insertion in the structurally robust spinel featuring small particle size and abundant cation vacancies, as evidenced by combined electrochemical measurements, XRD, Raman, synchrotron X-ray absorption spectroscopy, FTIR, and NMR analysis. The results would enlighten and promote the use of cation-defective spinel compounds and trifluoromethanesulfonic electrolyte to develop high-performance rechargeable zinc batteries.

SnO2-gated AlGaN/GaN high electron mobility transistors based oxygen sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hung, S.T.; Chung, Chi-Jung; Chen, Chin Ching

2012-01-01

Hydrothermally grown SnO2 was integrated with AlGaN/GaN high electron mobility transistor (HEMT) sensor as the gate electrode for oxygen detection. The crystalline of the SnO2 was improved after annealing at 400 C. The grain growth kinetics of the SnO2 nanomaterials, together with the O2 gas sensing properties and sensing mechanism of the SnO2 gated HEMT sensors were investigated. Detection of 1% oxygen in nitrogen at 100 C was possible. A low operation temperature and low power consumption oxygen sensor can be achieved by combining the SnO2 films with the AlGaN/GaN HEMT structure

Synthesis of magnetic Bi2O2CO3/ZnFe2O4 composite with improved photocatalytic activity and easy recyclability

NASA Astrophysics Data System (ADS)

Liu, Yumin; Ren, Hao; Lv, Hua; Guang, Jing; Cao, Yafei

2018-03-01

Magnetic Bi2O2CO3/ZnFe2O4 heterojunction photocatalysts with varying content of ZnFe2O4 were constructed by modifying Bi2O2CO3 nanosheets with mesoporous ZnFe2O4 nanoparticles. The photoactivity of the products was investigated by decomposing RhodamineB (RhB) and it was found that the photoactivity of Bi2O2CO3/ZnFe2O4 composite was closely related to the loading amount of ZnFe2O4. Under simulant sunlight irradiation, the optimum photoactivity of Bi2O2CO3/ZnFe2O4 composite was almost 2.3 and 2.1 times higher than that by bare ZnFe2O4 and Bi2O2CO3, respectively. The improved photoactivity resulted from the synergistic effect of Bi2O2CO3 and ZnFe2O4, which not only extended the photoabsorption region but also significantly facilitated the interfacial charge transfer. Besides the high photocatalytic performance, Bi2O2CO3/ZnFe2O4 composite also exhibited excellent stable and recycling properties, which enabled it have great potential in a long-term practical use.

Antibacterial studies of ZnO nanoparticle coatings on nanocrystalline YSZ irradiated with femtosecond laser light

NASA Astrophysics Data System (ADS)

Alvarez, Crysthal; Garcia, Valeria; Cuando, Natanael; Aguilar, Guillermo

2018-02-01

Recently, efforts have been made to create a transparent ceramic cranial implant comprised of nanocrystalline yttriastabilized zirconia (nc-YSZ) that will provide optical access to the brain. This has been referred to as Window to the Brain (WttB) in the literature. WttB will allow the use of laser and photonic treatments and diagnostics in areas with difficult optical access in the brain. Nevertheless, infection is still one of the frequent cranial implant complications. In most cases a second surgery is required to replace the infected implant. To address potential infections in the WttB platform, we have studied the antibacterial effect of a Zinc Oxide (ZnO) nanoparticles coating on nc-YSZ. After coating with ZnO nanoparticles, the implant was irradiated with infrared femtosecond laser light. We synthesized ZnO nanoparticles through the Laser Ablation of Solids in Liquids (LASL) method, using a Zinc solid target in a liquid medium (water/acetone). Antibacterial coatings were obtained by air brush, using a precursor solution of ZnO nanoparticles in distilled water. Escherichia coli (E. coli) have been used as representative, clinical relevant bacteria to probe the antibacterial effect of the coating. Our previous studies suggested that the use of ZnO nanoparticles inhibit bacterial growth. Laser irradiation treatment alone also offers inhibition of bacterial growth, up to 70%. The incorporation of nanoparticles offers an additional 20% inhibition. Thus, this work represents the next step towards the development of a clinically-oriented transparent cranial implant.

Synthesis of ZnGa2O4 Hierarchical Nanostructure by Au Catalysts Induced Thermal Evaporation

PubMed Central

2010-01-01

In this paper, ZnGa2O4 hierarchical nanostructures with comb-like morphology are fabricated by a simple two-step chemical vapor deposition (CVD) method: first, the Ga2O3 nanowires were synthesized and employed as templates for the growth of ZnGa2O4 nanocombs; then, the as-prepared Ga2O3 nanowires were reacted with ZnO vapor to form ZnGa2O4 nanocombs. Before the reaction, the Au nanoparticles were deposited on the surfaces of Ga2O3 nanowires and used as catalysts to control the teeth growth of ZnGa2O4 nanocombs. The as-prepared ZnGa2O4 nanocombs were highly crystallized with cubic spinel structure. From the photoluminescence (PL) spectrum, a broad band emission in the visible light region was observed of as-prepared ZnGa2O4 nanocombs, which make it promising application as an optical material. PMID:20802787

Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

NASA Astrophysics Data System (ADS)

Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

2015-06-01

Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

Excellent rate capability and cycling stability in Li+-conductive Li2SnO3-coated LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries.

PubMed

Mou, Jirong; Deng, Yunlong; Song, Zhicui; Zheng, Qiaoji; Lam, Kwok Ho; Lin, Dunmin

2018-05-22

High-voltage LiNi0.5Mn1.5O4 is a promising cathode candidate for lithium-ion batteries (LIBs) due to its considerable energy density and power density, but the material generally undergoes serious capacity fading caused by side reactions between the active material and organic electrolyte. In this work, Li+-conductive Li2SnO3 was coated on the surface of LiNi0.5Mn1.5O4 to protect the cathode against the attack of HF, mitigate the dissolution of Mn ions during cycling and improve the Li+ diffusion coefficient of the materials. Remarkable improvement in cycling stability and rate performance has been achieved in Li2SnO3-coated LiNi0.5Mn1.5O4. The 1.0 wt% Li2SnO3-coated LiNi0.5Mn1.5O4 cathode exhibits excellent cycling stability with a capacity retention of 88.2% after 150 cycles at 0.1 C and rate capability at high discharge rates of 5 C and 10 C, presenting discharge capacities of 119.5 and 112.2 mAh g-1, respectively. In particular, a significant improvement in cycling stability at 55 °C is obtained after the coating of 1.0 wt% Li2SnO3, giving a capacity retention of 86.8% after 150 cycles at 1 C and 55 °C. The present study provides a significant insight into the effective protection of Li-conductive coating materials for a high-voltage LiNi0.5Mn1.5O4 cathode material.

Effect of fluorine doping on highly transparent conductive spray deposited nanocrystalline tin oxide thin films

NASA Astrophysics Data System (ADS)

Moholkar, A. V.; Pawar, S. M.; Rajpure, K. Y.; Bhosale, C. H.; Kim, J. H.

2009-09-01

The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence of optical, structural and electrical properties of SnO 2 films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning electron microscope (SEM) and Hall effect studies have been performed on SnO 2:F (FTO) films coated on glass substrates. The film thickness varies from 800 to 1572 nm. X-ray diffraction pattern reveals the presence of cassiterite structure with (2 0 0) preferential orientation for FTO films. The crystallite size varies from 35 to 66 nm. SEM and AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the films are degenerate and exhibit n-type electrical conductivity. The 20 wt% F doped film has a minimum resistivity of 3.8 × 10 -4 Ω cm, carrier density of 24.9 × 10 20 cm -3 and mobility of 6.59 cm 2 V -1 s -1. The sprayed FTO film having minimum resistance of 3.42 Ω/cm 2, highest figure of merit of 6.18 × 10 -2 Ω -1 at 550 nm and 96% IR reflectivity suggest, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter electrode.

A novel approach for the synthesis of SnO2 nanoparticles and its application as a catalyst in the reduction and photodegradation of organic compounds.

PubMed

Bhattacharjee, Archita; Ahmaruzzaman, M; Sinha, Tanur

2015-02-05

Tin oxide (SnO2) nanoparticles of sizes ∼4.5, ∼10 and ∼30 nm were successfully synthesized by a simple chemical precipitation method using amino acid, glycine which acts as a complexing agent and surfactant, namely sodium dodecyl sulfate (SDS) as a stabilizing agent, at various calcination temperatures of 200, 400 and 600°C. This method resulted in the formation of spherical SnO2 nanoparticles and the size of the nanoparticles was found to be a factor of calcination temperature. The spherical SnO2 nanoparticles show a tetragonal rutile crystalline structure. A dramatic increase in band gap energy (3.8-4.21 eV) was observed with a decrease in grain size (30-4.5 nm) due to three dimensional quantum confinement effect shown by the synthesized SnO2 nanoparticles. SnO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and fourier transformed infrared spectroscopy (FT-IR). The optical properties were investigated using UV-visible spectroscopy. These SnO2 nanoparticles were employed as catalyst for the reduction of p-nitro phenol to p-amino phenol in aqueous medium for the first time. The synthesized SnO2 nanoparticles act as an efficient photocatalyst in the degradation of methyl violet 6B dye under direct sunlight. For the first time, methyl violet 6B dye was degraded by SnO2 nanoparticles under direct sunlight. Copyright © 2014 Elsevier B.V. All rights reserved.

BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell.

PubMed

Baek, Ji Hyun; Kim, Byeong Jo; Han, Gill Sang; Hwang, Sung Won; Kim, Dong Rip; Cho, In Sun; Jung, Hyun Suk

2017-01-18

Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO 4 /WO 3 /SnO 2 triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO 2 film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO 3 deposition, leading to the formation of a double layer of dense WO 3 and a WO 3 /SnO 2 mixture at the bottom. Subsequently, a BiVO 4 nanoparticle film was deposited by spin coating. Importantly, the WO 3 /(WO 3 +SnO 2 ) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO 4 /WO 3 heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm 2 at 1.23 V vs RHE) compared to the previously reported BiVO 4 /WO 3 photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO x electrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).

Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium.

PubMed

Guo, Xiaolei; Wan, Jiafeng; Yu, Xiujuan; Lin, Yuhui

2016-12-01

In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO 2 -TiO 2 /Nano-G) composite was synthesized by a sol-gel method and SnO 2 -TiO 2 /Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N 2 adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO 2 -TiO 2 /Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO 2 , SnO 2 and Nano-G were composited successfully, and TiO 2 and SnO 2 particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO 2 modified anode was higher than that of TiO 2 /Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO 2 -TiO 2 /Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO 2 -TiO 2 /Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO 2 -TiO 2 /Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO 2 -TiO 2 /Nano-G electrode. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-pressure phases transitions in SnO2 to 117 GPa: Implications for silica

NASA Astrophysics Data System (ADS)

Shieh, S. R.; Kubo, A.; Duffy, T. S.; Prakapenka, V. B.; Shen, G.

2005-12-01

Cassiterite (SnO2) is regarded to be a good analog material for silica as both SnO2 and SiO2 are group IV-B metal dioxides. The high-pressure behavior of SnO2 has been the subject of many previous investigations extending up to 49 GPa and in addition to the rutile structure, three high-pressure phases, CaCl2-type, α-PbO2-type, and pyrite-type were observed. Better knowledge of high-pressure phases of SnO2 will be useful to understand the behavior of silica at deep mantle conditions. In addition, high-pressure metal dioxide phases may qualify as superhard solids. Our study will also provide insights into interpretation of shock compression data. Pure natural cassiterite (SnO2) powder was compressed in a diamond anvil cell using an argon medium. Pressure was determined from the equation of state of platinum. In situ monochromatic x-ray diffraction at high pressure was carried out at the GSECARS, Advanced Photon Source. High temperatures were achieved using double-sided laser heating . Three heating cycles were conducted with total heating times up to 30 minutes. Our diffraction results on SnO2 demonstrate the existence of four phase transitions to 117 GPa. The observed sequence of high-pressure phases for SnO2 is rutile-type, CaCl2-type, pyrite-type, ZrO2 orthorhombic phase I (Pbca), cotunnite-type. Our observations of the first three phases are generally in agreement with earlier studies. The orthorhombic phase I and cotunnite-type structures were observed in SnO2 for the first time. The Pbca phase is found at 50-74 GPa during room-temperature compression. The cotunnite-type structure was synthesized when SnO2 was heated at 74 GPa and 1200 K. The cotunnite-type form was observed during compression between 54-117 GPa. Fitting the pressure-volume data for the high-pressure phases to the second-order Birch-Murnaghan equation of state yields a bulk modulus of 259(26) GPa for the Pbca phase and 417(7) GPa for the cotunnite-type phase. Rietveld profile refinements were